Assam HS Class 11-12 Logic and Philosophy key terms

A proposition that asserts or denies that all or some members of one class are included in another class, using the forms All S is P, No S is P, Some S is P, or Some S is not P.

The two features that classify categorical propositions: quantity is universal or particular (how much of the subject class is covered), and quality is affirmative or negative (whether inclusion or exclusion is asserted).

The four standard categorical proposition types: A (universal affirmative), E (universal negative), I (particular affirmative), and O (particular negative). Every categorical proposition in traditional logic is fitted into one of these.

A term is distributed when a proposition says something about every member of the class the term names. Universal subjects are distributed, and negative predicates are distributed; the other positions are undistributed.

A diagram arranging A, E, I and O propositions to show logical relations: contradictories differ in truth value, contraries cannot both be true, subcontraries cannot both be false, and subalternation passes truth down from universal to particular.

An immediate inference that swaps the subject and predicate of a proposition. It is valid for E and I propositions unchanged, and for A propositions only by limitation to the I form.

An immediate inference that changes the quality of a proposition and replaces the predicate with its complement. Obversion is valid for all four AEIO forms and preserves truth value.

An inference drawn from a single premise, without any intervening middle term, as in conversion, obversion, and the relations of the square of opposition.

A relation between two propositions that differ in both quantity and quality, so exactly one must be true and the other false; also, a statement that affirms and denies the same thing of the same subject.

A deductive argument with exactly two categorical premises and one categorical conclusion, containing three terms, each appearing in two propositions, where the premises jointly entail the conclusion.

The term that appears in both premises of a categorical syllogism but not in the conclusion; it links the major and minor terms and must be distributed at least once.

The figure of a syllogism is the arrangement of its middle term across the two premises; the mood is the sequence of AEIO proposition types. Together they identify a syllogistic form such as Barbara.

Conditions a valid categorical syllogism must satisfy, including: the middle term must be distributed at least once, no term may be distributed in the conclusion unless distributed in a premise, and two negative premises yield no conclusion.

A syllogistic fallacy in which a term is distributed in the conclusion but was undistributed in its premise, either the major term (illicit major) or the minor term (illicit minor).

An error in reasoning that makes an argument appear convincing when it is not. Formal fallacies depend on invalid logical form; informal fallacies depend on content, language, or irrelevant appeal.

The fallacy of begging the question, where the conclusion is assumed in the premises, often through restating the conclusion in different words or through a circular chain of reasoning.

The fallacy of irrelevant conclusion: an argument that proves something other than the point at issue and presents it as if the original claim had been established.

An informal fallacy that attacks the person making a claim, or that person's circumstances and motives, instead of addressing the evidence and reasoning offered for the claim.

The property of an expression that has more than one possible meaning in context. Fallacies of ambiguity, such as equivocation and amphiboly, exploit shifts between meanings within an argument.

A word or phrase that can serve as the subject or predicate of a proposition, standing for a class or an individual. Terms are the building blocks of categorical propositions.

Denotation is the set of objects a term applies to; connotation is the set of attributes an object must have to fall under the term. The two vary independently across terms.

A declarative statement that is either true or false. Propositions differ from sentences, questions, commands, and mere expressions of feeling, which are not truth-evaluable.

The truth or falsity of a proposition, conventionally written T and F. In propositional calculus every well-formed formula receives a truth value under each assignment of values to its variables.

An operator that combines simpler propositions into compound ones: negation (not), conjunction (and), disjunction (or), conditional (if-then), and biconditional (if and only if).

A systematic table listing every possible combination of truth values for the variables in a formula and the resulting value of the whole formula, used to test validity and classify formulas.

A formula that is true under every assignment of truth values to its variables. Its negation is a contradiction, and a formula true under some but not all assignments is contingent.

The truth function for 'if p then q', false only when the antecedent is true and the consequent false. This differs from the everyday idea of implication as a relation of meaning or causation.

A valid argument form: if p then q; p; therefore q. Affirming the antecedent guarantees the consequent. Its invalid look-alike, affirming the consequent, does not.

A valid argument form: if p then q; not q; therefore not p. Denying the consequent forces denial of the antecedent; denying the antecedent instead is a fallacy.

Reasoning that moves from particular observations to a general conclusion, or from known cases to probable predictions, yielding conclusions that are more or less probable rather than certain.

Five methods for discovering causal connections from observed cases: agreement, difference, joint method of agreement and difference, concomitant variation, and residues.

An inference that because two things resemble each other in known respects, they probably resemble each other in a further respect. Its strength depends on the number and relevance of shared features.

A proposed explanation or tentative generalization adopted for testing. In scientific method a hypothesis is confirmed or disconfirmed by deducing observable consequences and checking them against evidence.

The procedure of framing a problem, proposing hypotheses, deducing testable consequences, and verifying them by observation or experiment, with results feeding back into revised theory.

The branch of philosophy that investigates the most general features of reality: what exists, what kinds of things exist, and how they relate, including substance, causation, and identity.

The branch of philosophy concerned with knowledge: its nature, sources, scope, and limits, including the analysis of belief, truth, justification, and the problem of skepticism.

Monism holds that reality consists of one fundamental kind of thing; dualism holds that it consists of two, such as mind and matter. Both positions arise in Western and Indian metaphysics.

In Indian epistemology, a valid means of knowledge. Classical schools debate the number and status of pramanas, commonly perception, inference, comparison, and verbal testimony.

Perception as a source of knowledge in Indian philosophy, arising from contact between a sense organ and its object. Schools differ over whether it is always determinate or can be indeterminate.

Inference in Indian logic, knowledge of something not perceived derived from a sign or reason together with a remembered relation of invariable concomitance (vyapti) between sign and conclusion.

The relation of invariable concomitance between a sign and what it signifies, which grounds valid inference in Indian logic. Establishing vyapti, free of exceptions, is the central problem of inference.

In Samkhya, the two ultimate realities: Prakriti is unconscious primordial nature that evolves the world, and Purusha is pure consciousness, plural and inactive. Liberation is the discernment of their difference.