Every intellectual tradition builds its own vocabulary. The freethought tradition is no exception — but its vocabulary carries an unusual burden. These are not neutral academic terms. They are words that got people killed, words that were weaponised against the people who used them, and words that were eventually reclaimed.
The oldest word: atheism
Atheism is perhaps the most misunderstood term in the entire tradition. Its detractors define it as a dogmatic denial of God’s existence — a kind of anti-religion religion. Its defenders point out that it means nothing more than the absence of belief in gods. The distinction matters. One is a metaphysical claim; the other is simply a description of where someone has landed after examining the evidence.
The ancient Greeks used the word atheos to describe anyone who rejected the gods of the city. Socrates was charged with it. Early Christians were called atheists by the Romans because they refused to worship the Roman pantheon. The word has always meant “the wrong kind of believer” more than “no believer at all.”
Freethought and the Enlightenment
The term freethought emerged in the seventeenth and eighteenth centuries to describe a method rather than a conclusion. A freethinker was someone who insisted on forming beliefs about religion, morality, and metaphysics through reason and evidence rather than through tradition, authority, or revelation.
This distinction — between method and conclusion — is what separates freethought from atheism. An atheist has arrived at a particular answer. A freethinker has committed to a particular process. The two often overlap, but they are not the same thing. A deist like Thomas Paine was a freethinker who believed in God. A materialist like Baron d’Holbach was a freethinker who did not.
The careful agnostic
Agnosticism was coined by Thomas Henry Huxley in 1869, and it remains one of the most frequently misused terms in philosophy. It does not mean “I haven’t decided yet” or “I’m on the fence.” Huxley meant something much more precise: that the question of God’s existence falls outside the reach of human knowledge, and that intellectual honesty requires acknowledging this limitation rather than pretending to certainty in either direction.
This is a genuinely radical position. It does not grant atheism the easy confidence of certainty, and it does not grant theism the comfort of faith. It demands that we sit with not knowing — which, as anyone who has tried it can confirm, is harder than it sounds.
Rationalism versus empiricism
These two terms name a philosophical argument that predates the freethought movement but runs through it like a fault line. Rationalism holds that reason, independent of sensory experience, is the primary source of knowledge. Empiricism insists that all genuine knowledge derives from observation and experience.
Most freethinkers lean empiricist — David Hume, the patron saint of the tradition, certainly did. But the tension between the two positions is productive. Rationalism at its best produces the precise logical arguments of Bertrand Russell. Empiricism at its best produces the scientific method of Carl Sagan. The freethought tradition needs both.
Determinism and the question of free will
One of the less comfortable corners of freethought is determinism — the doctrine that every event, including every human thought and action, is the inevitable consequence of prior causes and natural laws. If the universe is governed by physical law, and the brain is a physical organ, then in what sense are our choices “free”?
This question has divided freethinkers for centuries. Some, like Sam Harris, argue that free will is simply an illusion. Others insist on a compatibilist position: that determinism and meaningful human agency are not in conflict. The vocabulary here matters enormously, because the answer you give shapes your views on morality, criminal justice, and personal responsibility.
The secular humanist synthesis
Secular humanism represents a relatively modern attempt to build an affirmative philosophy out of the freethought tradition. Rather than defining itself by what it rejects (gods, revelation, supernatural claims), it defines itself by what it affirms: human dignity, reason, ethics without reference to the supernatural, and the capacity of human beings to live well on the basis of natural capacities alone.
The term gained formal institutional backing in the twentieth century, but its roots are older. The idea that human flourishing does not require divine permission runs from Epicurus through Spinoza through Mill through Russell.
Materialism: the unfashionable position
Materialism is the metaphysical claim that everything that exists is physical — that matter and energy, operating according to natural laws, constitute the whole of reality. Mind, consciousness, and apparently non-physical phenomena are ultimately physical phenomena described in other terms.
This is the position that most working scientists hold implicitly, even if they would not describe themselves as materialists. It is also the position that most people find intuitively unsatisfying, because it seems to leave no room for the felt reality of consciousness, meaning, or purpose. Whether this dissatisfaction is a genuine philosophical objection or merely a failure of imagination remains, as the philosophers say, an open question.
Skepticism: the method beneath it all
If there is one word that unifies the entire freethought tradition, it is skepticism — the insistence that knowledge claims require evidence, and that many claims commonly accepted as knowledge fail to meet the standards that genuine knowledge demands.
Skepticism is not cynicism. The cynic doubts everything and believes nothing. The skeptic doubts in proportion to the evidence and believes in proportion to the proof. Hume was a skeptic. Sagan was a skeptic. The entire scientific method is an exercise in organised skepticism.
The vocabulary of unbelief is not a fixed lexicon. It grows, shifts, and occasionally contradicts itself — which is, perhaps, exactly what you would expect from a tradition that refuses to treat any text as final.