Branch of philosophy

Logic

What makes reasoning valid?

Test your reasoning

A quick test.

All birds can fly.
Penguins are birds.
Therefore, penguins can fly.

Does the conclusion follow from the premises?

The core

Logic is the study of valid reasoning — the science of what follows from what. It does not tell you what to believe; it tells you what your beliefs commit you to. If you accept certain premises, logic reveals what conclusions you are obliged to accept and which you must reject, regardless of your preferences, your emotions, or your cultural inheritance.

Aristotle formalised logic in the fourth century BCE through the syllogism: a three-part argument consisting of two premises and a conclusion. “All men are mortal; Socrates is a man; therefore Socrates is mortal” is the most famous example. The syllogistic system identified the valid forms of argument — the structures that guarantee true conclusions from true premises — and distinguished them from the invalid forms that merely appear to prove something.

Validity vs. soundness

The distinction between validity and soundness is the first and most important lesson logic teaches. An argument is valid if the conclusion follows necessarily from the premises — even if the premises are false. An argument is sound if it is valid and the premises are true. You can have perfect logic and a false conclusion (if your premises are wrong). You can also have true premises and an invalid argument (if your reasoning is flawed). Logic alone cannot tell you whether your premises are true — that requires evidence, observation, and judgement. What logic does is ensure that your reasoning does not introduce errors of its own.

Beyond Aristotle

Modern logic, beginning with Frege and Russell in the late nineteenth century, vastly expanded the scope of logical analysis. Propositional logic handles the relationships between whole statements (if P, then Q). Predicate logic handles the internal structure of statements (for all x, if x is F then x is G). Modal logic handles necessity and possibility. Each extension captures patterns of valid reasoning that Aristotle’s syllogistic system could not express.

The study of logical fallacies— invalid argument forms that are psychologically compelling — is equally important. Ad hominem (attacking the person rather than the argument), appeal to authority (treating someone’s status as evidence for their claims), false dilemma (presenting two options when more exist), circular reasoning (assuming what you set out to prove) — these are not merely technical errors. They are the operating system of most public discourse, and recognising them is a prerequisite for thinking clearly about anything.

In the Islamic tradition

Aristotelian logic was among the first Greek sciences translated into Arabic, and it became one of the most intensively studied disciplines in Islamic intellectual life. Al-Fārābī(d. 950), known as the “Second Teacher” (after Aristotle), produced commentaries and original works on logic that shaped the discipline for centuries. Ibn Sīnā (Avicenna) developed logic further, integrating it into his philosophical system and extending Aristotelian syllogistics in original directions.

The crucial turn came with al-Ghazali. In a move that surprised both his allies and his critics, al-Ghazali — the great critic of the philosophers — defended logic. In the introduction to his al-Mustaṣfā (on legal theory), he argued that logic is a neutral instrument: it does not commit you to any metaphysical position. Just as a scale does not determine what you weigh, logic does not determine what you believe — it only ensures that your reasoning is consistent. After al-Ghazali, logic became a standard part of the Islamic seminary curriculum, accepted even by scholars who rejected philosophy.

But there is an irony here. Logic was accepted as a tool and then largely confined to theological and juridical applications. The capacity for rigorous formal reasoning was preserved, but its scope was narrowed. Logic was used to defend established positions rather than to generate new ones — to demonstrate what was already believed rather than to discover what was not yet known. The tool survived; the culture of open inquiry that had produced it gradually did not.

Why this matters

Pakistan’s public discourse is saturated with logical fallacies — and almost no one notices. Political debate consists largely of ad hominem attacks and appeals to authority. Religious discussion relies on circular reasoning (“the text is true because it is divine, and it is divine because the text says so”) that would be immediately visible to anyone trained in basic logic. Media commentary confuses correlation with causation, anecdote with evidence, and assertion with argument. These are not signs of stupidity; they are signs of a society that never taught its citizens the most basic tools of rational evaluation.

The absence of logical training in Pakistan’s educational system is not an oversight; it is a structural feature of a system designed for reproduction rather than inquiry. Teaching logic means teaching students to evaluate arguments — including the arguments of their teachers, their textbooks, and their religious authorities. A system that depends on deference cannot afford to teach the tools that make deference optional.

Iqbal would have recognised this immediately. The recovery of ijtihad — independent reasoning — presupposes the capacity for valid reasoning. You cannot think independently if you cannot think correctly. Logic is not the whole of thinking, but without it, thinking becomes mere assertion — and assertion, however passionate, is not knowledge.

Connections

Epistemology Kalam (Islamic theology)

Appears in

Lecture I (Sections 1–4) · Lecture II (Sections 1–2)