Introduction to Philosophy & Logic (1999) #
A systematic introduction to Aristotelian logic and Thomistic philosophy. These lectures trace the natural progression of human knowledge from sensation to wisdom, examining the essential tools of logical reasoning—definition, division, and syllogistic demonstration—as presented in the works of Aristotle and St. Thomas Aquinas.
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Lectures #
1. The Natural Desire to Know and the Road to Wisdom #
This lecture explores Aristotle’s foundational claim that all men by nature desire to know, examining what this statement means, whether it is true, and why Aristotle begins his Metaphysics with it. Berquist traces the natural progression of human knowledge from sensation through memory, experience, and art/science, establishing how wisdom represents the culmination of this natural road and clarifying the philosophical virtue of humility regarding human wisdom in relation to divine wisdom.
2. Wisdom as Knowledge of Causes and First Principles #
Berquist expounds on Aristotle’s distinction between experiential knowledge (knowing that something is so) and scientific/artistic knowledge (knowing why it is so), establishing that wisdom consists in knowledge of causes. The lecture develops Aristotle’s six characteristics of the wise man and demonstrates how wisdom involves knowledge of what is most universal and most difficult to know, while paradoxically being more certain than other sciences. The analysis reveals wisdom as contemplative knowledge pursued for its own sake, fundamentally different from practical knowledge, and shows how all other sciences serve and are directed by wisdom.
3. The Order of Sciences and Certainty #
Berquist explores the hierarchical ordering of sciences according to their degree of certainty and abstraction, moving from arithmetic (most certain, most universal) through geometry and natural philosophy to practical philosophy (least certain, most particular). He demonstrates how the addition of matter to abstract principles reduces certainty, and applies this principle to understand why wisdom about first causes is most certain despite dealing with the most complex subject matter.
4. The Philosopher as Lover of Wisdom: Definition and Equivocation #
This lecture examines the definition of a philosopher in the original and true sense as a lover of wisdom (φιλόσοφος), distinguishing this from equivocal modern uses of the term. Berquist explores how modern thinkers—Bacon, Smith, Hegel, Sartre, and Nietzsche—have substituted other loves (power, wealth, freedom) for wisdom itself, arguing that true philosophy requires loving reason since wisdom is the highest perfection of reason. The lecture also addresses why the Greek philosophers, though lacking revelation, were not culpable in the way modern philosophers are for having access to divine wisdom through Christ yet rejecting it.
5. Four Natural Beginnings of Philosophy #
This lecture explores the four natural beginnings from which philosophy must commence: two in desire (wonder and the natural desire to live well) and two in knowledge (the natural road from senses to reason, and natural understanding of axioms). Berquist examines how the natural road progresses through sensing, memory, experience, and knowledge of universals, and establishes the order in which things are known—sensible before insensible, effects before causes, and composed before simple.
6. The Natural Road of Knowledge: From Examples to Definition #
This lecture explores how human knowledge naturally progresses from particular examples to universal definitions, and from outward (sensible) knowledge to inward (rational) knowledge. Berquist examines Socratic method, the relationship between induction and syllogism, and Aristotle’s paradoxical insight that what is more known to us is less fully known. The lecture emphasizes that philosophical progress requires understanding this natural ordering of knowledge.
7. Natural Beginnings of Philosophy and Following What Is Common #
This lecture explores why philosophy must begin from natural beginnings and why followers of truth must follow what is common rather than private understanding. Berquist develops the concept through Heraclitus’s fragments on the waking world, the teacher-student relationship, and scientific methodology, arguing that disagreement in philosophy arises precisely from departing from natural and common ground. The lecture emphasizes that the dispositions of will and emotion—wonder, humility, perseverance, fear of mistake—are necessary for the philosopher, and that civilization itself depends on following common law rooted in natural law.
8. Shakespeare’s Definition of Reason: Discourse and Capability #
This lecture analyzes Shakespeare’s exhortation to use reason from Hamlet, examining how it is written in blank verse and structured as a logical proportion. Berquist explores the definition of reason as ’the ability for large discourse, looking before and after,’ breaking down each component—ability (genus), discourse (first differentia), and large (second differentia)—to show how reason is fundamentally the capacity to know one thing through knowing other things, distinguishing it from mere sensation or imagination.
9. Reason as Large Discourse Looking Before and After #
This lecture provides a detailed philosophical analysis of Shakespeare’s definition of reason as “the ability for large discourse, looking before and after.” Berquist examines each component of this definition—ability, discourse, large, looking, and before/after—exploring how reason’s capacity for universal and causal understanding distinguishes it from mere sensation or imagination. The lecture emphasizes the multiple meanings of key terms (particularly the equivocal senses of “before”) and demonstrates how reason’s fundamental nature is tied to understanding order in all its dimensions.
10. Five Reasons to Use Reason: Philosophy and Human Flourishing #
Berquist analyzes Shakespeare’s exhortation to use reason by identifying five compelling reasons rooted in human nature and divine purpose. Through examination of references to God, man’s proper end, and authentic selfhood, the lecture demonstrates why reason is essential to human flourishing and why philosophy must proceed through the use of reason. The discussion connects reason to order, choice versus emotion, and what it means to be truly human.
11. Error, Wisdom, and the Four Senses of Before #
This lecture explores the nature of error and wisdom through etymological and philosophical analysis, focusing on how errors arise from either disordered reasoning or false imagination caused by likeness. Berquist develops a sophisticated account of four distinct senses of ‘before’ (temporal, essential, logical, and final causality) and demonstrates how wisdom consists in seeing what comes before and after in these various senses. The lecture culminates in showing how confusion between different senses of ‘before’ leads to equivocation and false reasoning.
12. The Three Acts of Reason and Logic’s Structure #
This lecture explores the three fundamental acts of reason—simple apprehension, composition/division, and reasoning—and their corresponding role in organizing the study of logic. Berquist explains how each act presupposes the previous one, how they relate to Aristotle’s logical works, and why logic serves as the essential tool for directing reason itself. The lecture also examines the relationship between the three acts and three corresponding tools (definition, statement, and syllogism) that perfect and order human reasoning.
13. Logic, Words, and the Ordering of Thought #
This lecture explores how logic functions as an art concerned with ordering our thoughts through the use of words. Berquist examines the relationship between the three acts of reason (definition, statement, and syllogism) and their corresponding tools, establishing that logic deals with vocal sounds insofar as they signify things and thoughts. The lecture emphasizes how reason, as a rational animal’s natural faculty, requires sensible signs—namely words—to order thinking about things we cannot directly sense or imagine.
14. Names Before Definition: The Art of Naming in Logic #
This lecture addresses why names must be studied before definitions in the logical order of knowledge. Berquist explains three reasons grounded in epistemology: we know things confusedly before distinctly, the question seeking definition presupposes understanding the name, and definitions are composed of names as parts. The lecture examines the definition of a name itself, distinguishes between calling things by their own names versus the names of other things (figurative speech), and introduces Porphyry’s five-fold distinction of names relative to definition.
15. Calling Things by Their Own Name: The Two Senses of ‘One’s Own’ #
Berquist resolves a central logical dilemma about definition: how can we define a thing by its own name when logic forbids using the name of the thing being defined in its definition? The solution lies in distinguishing two senses of ‘one’s own’—what belongs to me alone versus what belongs to me but not only to me. This distinction is crucial both for logic (enabling definition through common names) and for practical philosophy (understanding how we must see the common good as our own good).
16. Porphyry’s Five Names: Genus, Species, and Difference #
This lecture introduces Porphyry’s Isagoge and the five names (predicables) essential to logic: genus, species, difference, property, and accident. Berquist focuses primarily on genus, species, and difference—explaining how these names function in definition, how they relate to univocal predication, and how combinations of common names can create precise definitions that fit only one thing. The lecture explores the relative nature of the genus-species distinction and the concept of lowest species.
17. The Five Predicables: Genus, Species, Difference, Property, Accident #
This lecture explores Porphyry’s five predicables—the fundamental names used in logical definition. Berquist explains how genus, species, difference, property, and accident each relate to the nature of a thing, distinguishing those that are essential to definition from those that are accidental. The lecture introduces the crucial concept of relative distinctions, showing how the same name can function as both genus and species depending on what it is compared to, and raises ultimate questions about highest genera and lowest species.
18. The Five Predicables: Definitions and Distinctions #
This lecture explores the five predicables (genus, difference, species, property, and accident) as established by Porphyry’s Isagoge, examining their definitions, internal structures, and relationships to one another. Berquist demonstrates how each predicable shares common elements while differing in crucial ways, and shows how understanding these distinctions enables logicians to move from confused to distinct knowledge of things. The lecture addresses fundamental questions about whether every genus has a genus above it, whether multiple highest genera exist, and how definitions combine multiple differences to specify particular things.
19. Reasoning, Definition, and the Categories of Being #
This lecture explores the nature of reasoning and definition as ways of coming to know through what is already known, examines the categorical system for understanding how things are said of substances, and discusses the fundamental distinction between substance and accident. Berquist addresses how the ten Aristotelian categories relate to material composition (matter and form), the equivocity of being, and the theological implications of this metaphysical framework for understanding transubstantiation.
20. Highest Genera and the Distinction Between Substance and Accident #
This lecture explores how the highest genera (genera with no genus above them) are distinguished, arguing that multiple highest genera must exist because the word ‘being’ is equivocal rather than univocal. Berquist demonstrates that substance and accident represent fundamentally different ways of being, and uses Aristotle’s categorical framework to show how all other categories relate to individual substances.
21. The Ten Categories and the Five Predicables #
This lecture introduces Aristotle’s ten categories as the highest genera of being, explaining how they function as fundamental divisions of substance and accidents. Berquist explores the distinction between the five predicables (genus, species, difference, property, accident) from Porphyry’s Isagoge and the ten categories themselves, demonstrating their essential role in definition, division, and demonstration. Special attention is given to substance, quantity (discrete vs. continuous), quality, and relation, with emphasis on how the categories structure philosophical reasoning.
22. Equivocal Names, Figurative Speech, and Their Philosophical Functions #
This lecture explores two interconnected topics: equivocal names (words with multiple meanings connected by reason rather than chance) and the five main types of figurative speech in philosophy and theology. Berquist explains how equivocal names function in philosophical discourse, particularly in axioms and universal concepts, and then analyzes synecdoche, antonomasia, metonymy, metaphor, and irony as essential tools for understanding Scripture and philosophical texts. The lecture emphasizes that recognizing figurative language prevents heretical misinterpretations and allows an intelligent listener to discern the speaker’s true meaning beneath the surface of words.
23. Equivocal Names by Reason: Division and Carrying Over #
This lecture explores how names become equivocal by reason (analogous names), distinguishing this from purely equivocal naming by chance. Berquist systematizes two primary ways names acquire multiple connected meanings: through division (when one thing keeps a common name while another receives a new name) and through carrying over (when a name is transferred from one thing to another via generalization or ratio). The lecture demonstrates these mechanisms through extensive examples from daily speech, philosophy, and theology, emphasizing the rational basis underlying such equivocations.
24. Equivocation, Metaphor, and Figures of Speech #
This lecture explores the distinction between equivocal naming (particularly equivocation by reason) and metaphor, examining how these differ in their distance from univocal meaning and their use in various disciplines. Berquist analyzes why metaphor is appropriate to both poetry and sacred scripture for different reasons, explores several types of figures of speech (metonymy, synecdoche, and antonomasia), and demonstrates how philosophical and theological discourse employ these linguistic devices differently. The lecture includes detailed analysis of examples from Shakespeare, Gregory the Great, and scripture, and concludes with a discussion of how reason progresses from confused to distinct knowledge.
25. Definition: Nature, Kinds, and Distinctions #
This lecture explores the nature of definition as speech signifying what a thing is, establishing three formulations of definition and examining critical distinctions among types of definitions. Berquist emphasizes that definition is a major philosophical accomplishment requiring deep intellectual work, not merely linguistic clarification, and presents three fundamental distinctions: definition in the full sense versus encircling, definition by cause versus definition by effect, and definition of substance versus definition of accident.
26. Definition: Cause, Effect, Substance, and Accident #
This lecture explores three fundamental distinctions in logical definition: (1) definition by cause versus definition by effect, (2) definition in the full sense versus encircling definition, and (3) definition of substances versus definition of accidents. Berquist emphasizes that the cause-effect distinction is critical for understanding ethics, metaphysics, and the nature of reality itself, using examples from Socratic questioning about the good and the beautiful, and demonstrating why definitions must be adapted to the kind of thing being defined.
27. Three Ways of Investigating Definition #
Berquist explores three distinct starting points for investigating what something is: beginning from the more universal (genus and dividing downward), from the less universal or singular (examples and comparing upward), and from the equally universal (properties and reasoning inward). Each path employs different logical operations—division, comparison, and reasoning—and requires genuine thinking rather than mechanical procedure. The lecture emphasizes that defining is fundamentally different from calculation and that all three approaches may be used together to penetrate to the essence of a thing.
28. Division, Distinction, and the Rule of Two or Three #
This lecture explores the logical distinction between division and distinction, examining two kinds of wholes (integral/composed and universal), and establishing Berquist’s ‘rule of two or three’ for proper division. Drawing on Platonic binary divisions and Hegelian ternary divisions, Berquist argues that most natural divisions fall into either two or three parts, with divisions into more than three typically involving crossed divisions or subdivision. The lecture culminates in a principle of higher knowledge: it belongs to the higher and wiser discipline to distinguish itself from lower knowledge and establish order between them.
29. Distinctions in Logic: Per Se, Equivocation, and Qualified Being #
This lecture covers three fundamental types of distinctions in logic that are not strict divisions of wholes into parts: distinctions of word senses (equivocation), distinctions between per se and per accidens (through itself and through happening), and distinctions between what is simply and what is so in a qualified sense. Berquist emphasizes how these distinctions are critical for avoiding common logical errors and demonstrates their application through examples from desire, definition, and knowledge.
30. Truth and Falsity in Simple Statements #
This lecture explores the fundamental nature of truth and falsity in simple affirmative and negative statements. Berquist establishes that truth is the conformity of mind with things—saying what is, is, and what is not, is not—and identifies two modes of falsity: addition (saying what is not, is) and subtraction (saying what is, is not). Through courtroom testimony, theological examples (Trinity and Incarnation), and literary quotations, he demonstrates that truth operates as a mean between these two extremes and that contradictory statements necessarily have opposite truth values.
31. Truth and Falsity in Compound Statements #
This lecture explores how truth and falsity function in compound statements—specifically conditional (if-then) and disjunctive (either-or) statements—which operate according to different logical principles than simple statements. Berquist demonstrates that truth in conditionals depends on necessary consequence between antecedent and consequent, while truth in disjunctives depends on exhausting all possibilities. He argues that the meaning of ’true’ is equivocal across these contexts, related but fundamentally distinct from truth in simple statements.
32. The Square of Opposition and Contradictory Statements #
This lecture explores the logical relationships between universal and particular statements through the square of opposition, focusing on how contradictory statements differ from contrary statements. Berquist examines the critical distinction that only diagonal statements in the square (universal affirmative with particular negative, and universal negative with particular affirmative) are true contradictories—meaning one must be true and one must be false regardless of subject matter. The lecture also introduces the logic of the third act and begins examining reasoning as a form of movement of the mind, contrasting it with simple understanding.
33. Reasoning, Guessing, and the Four Arguments #
This lecture examines the nature of reasoning as the discursive movement from known or accepted statements to new statements, distinguishing it from understanding. Berquist introduces the four types of arguments (example, induction, enthymeme, and syllogism) as a progression along the ‘road from the senses into reason,’ emphasizing the relationship between certainty, necessity, and the strength of various forms of argumentation. The lecture explores how reasonable guessing operates in fields from meteorology to rhetoric, and how formal logic mirrors natural processes of production.
34. Etymology and Structure of the Four Arguments #
This lecture explores the etymological foundations and structural distinctions of the four arguments—example, induction, enthymeme, and syllogism—tracing their Greek and Latin names and examining how they relate to universal and particular reasoning. Berquist emphasizes the distinction between arguments that produce necessary conclusions (syllogism) and those that produce probable conclusions (the other three), using Shakespearean examples and linguistic analysis to clarify these foundational logical concepts.
35. Logic, Rhetoric, and Argumentation in Philosophy #
This lecture explores the foundational distinctions between logical and rhetorical arguments, examining four types of argumentation (syllogism, enthymeme, induction, and example) and classifying them both by likeness and usefulness. Berquist emphasizes how syllogism and induction serve philosophical inquiry into universals, while enthymeme and example serve rhetorical persuasion about particulars. The lecture illustrates these distinctions through detailed analysis of Shakespeare’s Othello, classical examples, and practical applications in various contexts of human reasoning and persuasion.
36. The Four Forms of Hypothetical Syllogisms #
This lecture examines the four forms of hypothetical (if-then) syllogisms, distinguishing between valid and invalid forms. Berquist demonstrates why two forms necessarily yield valid conclusions while the other two do not, emphasizing the problem of ‘false imagination’ that leads students to mistake invalid forms for valid ones. The lecture explores the concept of necessity in logic and illustrates these forms through mathematical, geometric, and everyday examples, including their application in Plato’s Meno dialogue.
37. The Four Forms of Hypothetical Syllogism and Scientific Confirmation #
This lecture examines the four possible forms of hypothetical (if-then) syllogisms, demonstrating that only two forms are valid syllogisms while the other two are fallacious. Berquist explains how the invalid forms deceive the human mind through false imagination, and applies this analysis to show why scientific hypothesis confirmation, using an invalid form, can never establish necessary truth. The lecture also distinguishes between the either-or syllogism and the if-then syllogism, with emphasis on the superiority of hypothesis rejection over confirmation in terms of logical rigor.
38. The Simple Categorical Syllogism and the Three Figures #
This lecture examines the structure of the simple categorical syllogism, focusing on how three terms are arranged across two premises to produce a necessary conclusion. Berquist analyzes the three figures determined by the position of the middle term, introduces the foundational principles of the dictum de omni and dictum de nullo, and begins exploring the sixteen possible combinations of premises in the first figure to identify which yield valid conclusions.
39. Validity and Invalidity in First Figure Syllogisms #
This lecture examines the sixteen possible categorical syllogisms in the first figure, demonstrating which forms are valid through the application of the two fundamental principles (dictum de omni and dictum de nullo) and which are invalid through systematic counterexamples. Berquist focuses on how to recognize valid syllogisms immediately when the set of all or set of none applies to the premises as stated, and how to disprove invalid forms by constructing concrete examples that satisfy both necessary conditions for invalidity.
40. The Second Figure: Conversion and Validity #
This lecture focuses on the second figure of the syllogism, where the middle term serves as the predicate in both premises. Berquist examines which forms are valid and which are not by analyzing how conversion of propositions allows imperfect syllogisms to be reduced to the first figure. He emphasizes the set of all and set of none as criteria for validity, and demonstrates the method of using counterexamples to test whether a syllogistic form necessarily yields a conclusion.
41. The Second Figure of the Syllogism and Conversion #
This lecture examines the second figure of the categorical syllogism, where the middle term appears as the predicate in both premises. Berquist demonstrates the four valid forms in the second figure, explains why only negative conclusions can be drawn, and develops the crucial doctrine of conversion—particularly the necessary conversion of universal negative statements. The lecture establishes why the second figure requires conversion to make logical necessity apparent, making these syllogisms ‘imperfect’ compared to the first figure.
42. Syllogistic Form in the Second Figure and Applications #
This lecture focuses on the valid forms of syllogistic reasoning in the second figure and their practical applications. Berquist works through examples of finding valid syllogistic combinations, discusses why certain premise combinations fail to yield valid conclusions, and demonstrates how theological and philosophical arguments employ second-figure syllogisms. The lecture also explores the broader relationship between natural bonds (brotherhood, sisterhood) and their supernatural counterparts, using literary and theological examples.
43. Demonstration, Necessity, and the Perfect Argument #
This lecture explores Aristotle’s account of demonstration (apodeixis) as the perfect form of syllogistic argument, emphasizing its intimate connection to cause, necessity, and definition. Berquist traces how demonstration differs fundamentally from dialectical reasoning, examines the role of ‘per se’ (through itself) and limit in ensuring knowledge rather than mere opinion, and shows how these principles structure the inquiry into ‘what’ and ‘why’ in speculative knowledge.
44. Sophistical Refutations and the Fallacy of Equivocation #
This lecture examines Aristotle’s account of sophistical refutations as deceptive arguments, focusing on the 13 fallacies Aristotle identifies—six arising from language and seven from things. Berquist emphasizes equivocation (confusing different senses of a word) as the most common mistake in thinking, illustrating how sophists exploit ambiguous language to deceive. The lecture also introduces amphiboly (ambiguous phrases) and traces how these fallacies relate to fundamental philosophical distinctions.
45. The Fallacy of the Accident and Its Deceptions #
This lecture explores the fallacy of the accident (fallacies accidentis), a fundamental logical error where what is necessarily present is mistaken for the true cause or essential property. Berquist emphasizes that this fallacy deceives even the wise, illustrating how the distinction between per se (through itself/as such) and per accidens (by happening/accidentally) is crucial for avoiding sophisticated deceptions in logic, natural philosophy, and theology. Multiple examples demonstrate how this confusion operates across language, causation, and human judgment.
46. Logic and Syllogistic Reasoning in Geometry and Theology #
This lecture examines the practical application of syllogistic logic across disciplines, focusing on how syllogisms are used to construct proofs in geometry and establish theological truths. Berquist demonstrates that eight fundamental syllogistic forms (four categorical, two conditional, two disjunctive) recur throughout philosophical and theological reasoning, illustrating their use through Euclid’s geometric proofs and Thomas Aquinas’s theological arguments.
47. Analysis of Complex Arguments: Syllogistic Structure and Forms #
This lecture demonstrates how to analyze complex philosophical and mathematical arguments by identifying their underlying syllogistic structures. Berquist examines Thomas Aquinas’s argument on the causes of love and several propositions from Euclid’s Elements to show how multiple syllogisms—categorical, conditional (if-then), and disjunctive (either-or)—work together in a single demonstration. The central pedagogical goal is teaching students to work backward from a conclusion to identify the main syllogism and the supporting syllogisms that establish its premises.
48. Demonstration, Dialectic, and the Matter of the Syllogism #
This lecture examines the two main kinds of syllogisms—demonstration and dialectical reasoning—and the importance of their premises. Berquist explains how demonstration reasons from necessarily true premises to necessary conclusions, while dialectical syllogisms reason from probable opinions to conclusions that may be probable but not necessary. He explores how both forms use the same eight fundamental syllogistic structures but differ crucially in the truth status and certainty of their premises.
49. Necessity, Per Se, and the Four Tools of Dialectic #
This lecture explores the fundamental connection between necessity and the concept of per se (as such/through itself) in Aristotelian logic, examining how necessary truths belong to things through their nature and definition. Berquist then introduces the four tools of the dialectician—selecting probable premises, distinguishing word senses, seeing differences, and seeing likenesses—establishing the foundation for dialectical reasoning as opposed to demonstrative proof. The lecture emphasizes how mastery of these tools enables proper philosophical inquiry and argumentation.
50. The Second Tool of Dialectic: Distinguishing Word Senses #
This lecture focuses on the second of Aristotle’s four tools of dialectic: the ability to distinguish the multiple senses or meanings of words. Berquist explains how equivocation—using words in different senses without distinction—is the most common mistake in thinking and the primary source of sophistic fallacy. Through extensive examples (dry, liberal, number, healthy, good, science), he demonstrates methods for identifying equivocal words by examining their opposites or their use in combination, and explains why this skill is essential for both clarity of thought and avoiding deception.
51. Proportion in Philosophy, Science, and Theology #
This lecture explores the foundational role of proportion (analogia) across all domains of knowledge—from natural science through metaphysics to theology. Berquist demonstrates how the inverse square law in physics, Platonic and Aristotelian philosophy, moral virtue, and theological doctrine all depend on recognizing proportional likenesses between different domains. The lecture emphasizes proportion as a critical tool for understanding definitions, syllogisms, and metaphors, and shows how failure to perceive proper proportions leads to philosophical error.
52. Three Fundamental Distinctions and Common Philosophical Fallacies #
This lecture focuses on three foundational distinctions in Thomistic philosophy: being simply versus being in a qualified way (simpliciter vs. secundum quid), substance versus accident, and act versus potentiality. Berquist demonstrates how confusion of these distinctions leads to common logical and metaphysical errors, and illustrates their application through concrete examples ranging from everyday situations to moral theology, emphasizing their critical importance throughout all philosophical inquiry.