Today I continued reading Hobbes’s Leviathan, reaching Chapter V, “Of Reason, and Science.” In the previous chapters, Hobbes had already taken me through sense, imagination, memory, thought and speech. Now he asks what happens when we take the names created through speech and begin to work with them. His answer is reason. But what interested me most was not simply his explanation of how we reason. It was his warning that the very ability that allows human beings to discover truth also gives us an extraordinary ability to construct absurdity.

For Hobbes, reason is not some mysterious light placed inside us at birth. He describes it almost mathematically: to reason is to reckon, to add and subtract. We join one proposition to another, consider what follows from what, and eventually arrive at a conclusion. The mathematician reckons with numbers; the rational mind reckons with names and their consequences. A conclusion therefore does not suddenly appear from nowhere. It is the end of a journey whose direction was determined much earlier.

This immediately raises a problem. If the words with which we begin are confused, what happens to everything we build from them?

Hobbes’s answer is severe: we can arrive at absurdity. Intelligence alone does not protect us, because a chain of reasoning may appear sophisticated while beginning from words that were never properly defined. Once ambiguity enters at the beginning, reason can carry it forward. In fact, the better we become at arguing from confused foundations, the more elaborate our confusion can become.

Hobbes makes this point sharply when discussing philosophical writing and recalls Cicero’s remark that there can be nothing so absurd that it cannot be found in the books of philosophers. It is an uncomfortable accusation, particularly in a chapter devoted to reason. We normally imagine that absurdity belongs to the person who does not think. Hobbes shows us another possibility: absurdity can be produced by thinking badly from words we have never properly understood.

That observation feels remarkably modern. How often do arguments continue for hours because two people use the same word differently? We argue about freedom, justice, success, morality, equality, love or truth as though the sound of a word guarantees a shared meaning. Sometimes we defend positions before asking ourselves what the central words actually mean. The argument becomes more complicated, more passionate and apparently more intellectual, while the original ambiguity remains untouched. Perhaps we are not disagreeing about the conclusion at all. Perhaps we began from different meanings.

This is why Hobbes places so much importance on names. In his account, words can serve as marks, allowing us to record thoughts for ourselves, and as signs, allowing us to communicate those thoughts to others. Language gives human thought extraordinary power because we are no longer imprisoned within the immediate experience. We can preserve what we discover, communicate it and allow another mind to continue where ours stopped. But the same instrument carries a danger. A badly used name does not merely describe confusion; it can become the foundation upon which further confusion is built.

The solution for Hobbes is definition and method. His image is beautiful: the light of the human mind is made from clear words, but those words must first be trimmed by exact definitions and cleansed of ambiguity. Language does not automatically illuminate thought. An undefined word can create smoke rather than light.

This also explains why Hobbes refuses to treat reason as something simply born within us. Sense and memory come naturally; prudence develops through experience. Reason requires industry. We must learn to impose names properly, define them carefully and proceed in an orderly manner from one consequence to another. Reason, then, is not merely the possession of intelligence. It is a discipline in how we move from what we have established towards what we claim to know.

Here Hobbes develops an important distinction between prudence and science. Experience teaches us what has happened before, and from repeated experience we become better at anticipating what may happen again. This is prudence. An experienced person recognises patterns that an inexperienced person misses. Yet those signs remain uncertain. The fact that something followed a particular course many times does not guarantee that it must do so again. Experience gives us expectation, not necessity.

Science goes further. It seeks the consequences of things and reduces them into general rules. Earlier in Leviathan, Hobbes distinguished human beings from other animals partly through our ability to inquire into consequences. Here he takes that ability another step: we do not merely notice that one event followed another; through reason we can search for general relations and preserve them as rules, theorems or aphorisms. Instead of knowing only what happened, we begin asking what follows from what, and why?

The distinction matters because experience can make a person prudent without making them scientific. Someone may become remarkably good at predicting situations simply because they have encountered them many times. Their judgment may even be better than that of someone with greater theoretical knowledge. But their prediction remains tied to signs from the past. Science attempts something different: an ordered knowledge of consequences.

Hobbes therefore gives us a progression that has been developing throughout these opening chapters of Leviathan. We sense the world. Imagination retains what sensation leaves behind. Memory preserves experience. Thought moves from one conception to another. Speech gives names to those conceptions and allows us to preserve and communicate them. Reason begins to reckon with those names. Science then takes discovered consequences and turns them into general knowledge.

But Hobbes does not allow this journey to end with knowledge itself. He writes that reason is the pace, the increase of science is the way, and the benefit of mankind is the end. That final part matters. Reason is movement; science is the road created by that movement; but knowledge must eventually lead somewhere beyond itself.

This is perhaps what I find most valuable in the chapter. We often admire thinking for its complexity. Hobbes forces us to ask whether complexity has been built upon clarity. A long argument is not necessarily a sound argument. A difficult book is not necessarily a wise book. An educated person is not necessarily reasoning well. If the first words are confused, everything that follows may simply be confusion made more impressive.

There is also something humbling in this. Reason is one of the abilities by which human beings exceed other animals, yet it also gives us a peculiar capacity for absurdity. An animal may misjudge what it experiences, but it does not construct philosophical systems from words whose meanings it has forgotten to examine. Our greatest intellectual instrument carries within it the possibility of a distinctly human failure.

Perhaps this is why definitions matter far beyond philosophy. Before defending an idea, we should know what we mean by it. Before following an argument, we should examine where it begins. Before becoming impressed by a conclusion, we should travel backwards through the reasoning that produced it.

Reason does not become reliable merely because we are intelligent. It becomes reliable through discipline: clear names, exact definitions, orderly movement and the willingness to return to the beginning when the conclusion becomes absurd.

The lesson I take from Hobbes is therefore not simply that we should reason more. Sometimes we already reason too much from foundations we have never examined. The better question is whether the words beneath our reasoning can bear the weight we place upon them.

Before adding another argument, return to the first word.

Define it.

Then reason.