Where does the idea of cause come from?
On the axis: Source of knowledge · the idea of cause
Empiricism would trace every idea back to a sense impression. But when one ball strikes another, we see only two motions in succession, never the force or the necessary link between them: where, then, does the idea of cause come from?
Justification
Perceptions fall into two classes set apart by their force alone: impressions, vivid and original (sensations, passions), and ideas, their faint copies in thought. From this Hume draws both a principle and an instrument: every simple idea derives from a prior impression, so an idea answering to no impression is empty of meaning. More radical than 's , this test does not merely reject : it becomes an engine for dissolving the pseudo-concepts of metaphysics (substance, necessary connection), which one need only challenge to produce their source impression. Empiricism is thus turned into a critical weapon against the of .
All our ideas are nothing but copies of our impressions, or, in other words, it is impossible for us to think of anything which we have not antecedently felt.Enquiry Concerning Human Understanding, sect. II
Enquiry Concerning Human Understanding, sect. II (of the origin of ideas) · A Treatise of Human Nature, I, part I, sect. 1
Justification
Every idea must derive from an impression: so Hume asks which impression yields the necessary connection between a cause and its effect, and finds none. In objects, experience gives only succession and constant conjunction; never the bond that would oblige one to follow the other. Necessity is therefore not in things: it is a habit (custom) of the mind, an expectation projected by repetition. Hence the problem of : if nothing lets us perceive the causal link, no inference from past to future is rationally grounded. It is this analysis, by undermining causation as objective necessity, that would rouse from his dogmatic slumber. and vital force, answering to no impression, fall with it.
After a repetition of similar instances, the mind is carried by habit, upon the appearance of one event, to expect its usual attendant... This connexion, therefore, which we feel in the mind, is the impression from which we form the idea of power or necessary connexion.Enquiry Concerning Human Understanding, sect. VII
Enquiry Concerning Human Understanding, sect. VII (of the idea of necessary connexion) · A Treatise of Human Nature, I, part III, sect. 6 and 14
Justification
The dispute between and is insoluble so long as one term is asked to carry everything: experience alone never yields necessity ('s objection about causation), reason alone runs idle. Kant's answer is the synthetic a priori judgment: there are a priori forms of sensibility and understanding that structure any possible experience, so that knowledge begins with experience without deriving wholly from it. This is the Copernican turn applied to knowledge, and the reason the axis settles at the centre.
Thoughts without content are empty, intuitions without concepts are blind.Critique of Pure Reason, A51/B75
Critique of Pure Reason, Introduction · Critique of Pure Reason, A51/B75
Justification
Causality is an a priori category of the understanding that structures every phenomenon by mechanical law: known nature is a chain of cause and effect. The third Critique adds purposiveness, but Kant declares it merely regulative, a principle for judging living things rather than a mechanism of the world, hence a minority finalist weight.
Critique of Pure Reason, Second Analogy of Experience · Critique of the Power of Judgment, §§61-68
leads to: Explaining nature