Kant Quote on the A Priori: Knowledge That Begins With Experience

Quote

"All knowledge begins with experience, but not all knowledge arises out of experience."

— Immanuel Kant, Critique of Pure Reason (Introduction, B1, 1787)

Context

This sentence opens the Introduction to the Critique of Pure Reason (in the second, 1787 edition, at B1), and it sets the stage for the entire project of transcendental philosophy. Kant is responding to the deadlock between empiricism and rationalism that had dominated modern philosophy since Locke and Leibniz.

The empiricists held that all knowledge derives from experience: the mind begins as a blank slate, and everything in it is supplied by the senses. The rationalists held that some knowledge is independent of experience — that reason alone can discover necessary truths about reality. Kant agrees with the empiricists that no knowledge begins without experience: there must be something that awakens the cognitive faculties into activity, and that something is the impingement of objects on the senses. But he agrees with the rationalists that not all knowledge arises from experience in the sense of being derived from it — some knowledge has a source in the mind's own structure.

The distinction between "beginning with" and "arising out of" experience is the wedge that opens the space for the a priori. Kant will go on to argue that the mind contributes forms of intuition (space and time) and categories of the understanding (cause, substance, and the rest) that are not learned from experience but that structure every possible experience. These a priori elements are what make experience itself possible.

Meaning

Kant's claim has two parts that must be held together:

"All knowledge begins with experience": No human being has knowledge prior to any encounter with the world. The senses must first be affected by objects for the mind to begin its work. Kant concedes to empiricism that experience is the occasion — the temporal starting point — of all cognition. A mind with no sensory input would have nothing to think about; its conceptual machinery would idle without material.

"But not all knowledge arises out of experience": Although experience starts the process, it does not supply all the content of knowledge. Some of what we know is contributed by the mind itself, independently of particular experiences. Kant calls this a priori knowledge — knowledge that is, in some sense, prior to and independent of experience, even though it only comes into play when experience awakens the mind.

The crucial move is Kant's distinction between a posteriori knowledge (derived from experience) and a priori knowledge (independent of experience), and within the a priori, between analytic judgments (true by virtue of meaning alone, like "all bachelors are unmarried") and synthetic judgments (substantive, informative). Kant's revolutionary thesis is that there are synthetic a priori judgments — substantive truths knowable independently of experience — such as the propositions of mathematics and the fundamental principles of natural science (e.g., that every event has a cause). These do not arise from experience; they are the conditions that make experience possible.

Philosophical Significance

Kant's distinction is the keystone of the Critique and of modern epistemology:

The synthetic a priori: By arguing that some substantive knowledge is independent of experience, Kant carved out a middle path between empiricism and rationalism. Mathematics, the principles of natural science, and the categories of the understanding are synthetic (they add to our knowledge) yet a priori (they are not learned from experience). This thesis dominated nineteenth-century philosophy and, though challenged by Quine's attack on the analytic-synthetic distinction in the twentieth century, remains a live option in contemporary debates about mathematical and modal knowledge.

The conditions of possible experience: The a priori elements are not free-floating certainties but conditions of experience. Space and time are the forms of sensibility; the categories are the forms of understanding. We know these a priori because they structure every experience we could possibly have. This "transcendental" turn — asking what must be true for experience to be possible — became the model for a vast tradition of philosophical inquiry, from German Idealism through phenomenology to contemporary "transcendental arguments."

The limits of knowledge: Because a priori knowledge concerns the conditions of possible experience, it applies only within experience, not beyond it. We can know a priori that every appearance has a cause, but we cannot know anything about things as they are in themselves, beyond the forms of our cognition. This boundary — limiting knowledge to make room for morality and faith — is one of Kant's most influential and most contested legacies.

Hume's challenge answered: Kant credited Hume with awakening him from "dogmatic slumber" by showing that causation cannot be derived from experience. The present dictum is Kant's reply: causation does not arise from experience — it is an a priori category that the mind brings to experience, making the very idea of an objective sequence of events possible. Hume was right that experience cannot teach necessity; Kant's answer is that necessity is not learned but supplied by the understanding.

Sources

1. Kant, Immanuel. Critique of Pure Reason, trans. P. Guyer and A. Wood (Cambridge University Press, 1998), Introduction, B1. Context in: https://plato.stanford.edu/entries/kant/
2. "Immanuel Kant," Stanford Encyclopedia of Philosophy. Available at: https://plato.stanford.edu/entries/kant/
3. "Immanuel Kant," Internet Encyclopedia of Philosophy. Available at: https://iep.utm.edu/kant/
4. "The Synthetic A Priori," Stanford Encyclopedia of Philosophy (within Kant entry). Available at: https://plato.stanford.edu/entries/kant/
5. Guyer, Paul. Kant and the Claims of Knowledge (Cambridge University Press, 1987).