Although the early Kant showed a complete willingness to dissent from many important aspects of the Wolffian orthodoxy of the time, Kant continued to take for granted the basic rationalist assumption that metaphysical cognition was possible. In a retrospective remark from the Prolegomena to Any Future Metaphysics (1783), Kant says that his faith in this rationalist assumption was shaken by David Hume (1711-1776), whose skepticism regarding the possibility of knowledge of causal necessary connections awoke Kant from his “dogmatic slumber” (4:260). Hume argued that we can never have knowledge of necessary connections between causes and effects because such knowledge can neither be given through the senses, nor derived a priori as conceptual truths. Kant realized that Hume’s problem was a serious one because his skepticism about knowledge of the necessity of the connection between cause and effect generalized to all metaphysical knowledge pertaining to necessity, not just causation specifically. For instance, there is the question why mathematical truths necessarily hold true in the natural world, or the question whether we can know that a being (God) exists necessarily.
The “class of intentional actions is a sub-class,” according to Anscombe, of “the class of things known without observation,” (Anscombe 2000, p. 14). Intentional actions are ones done for some reason, actions about which it makes sense to ask “Why?” and expect an answer that is not merely causal but explains what significance the action was taken to have for the agent. The intention is not itself a cause because causes (for example, a brick’s striking a window) are distinct from their effects (for example, the window’s breaking), whereas intentional actions are not distinct from the intentions they embody. To see this point more clearly, imagine a climber who loses the will to live and so lets go of the rock and falls to his death. This was intentional, an act of suicide. Now imagine that he simply loses his grip and falls. This is unintentional and not suicide but a tragic accident. Now imagine that he has a momentary suicidal impulse. Shocked by this thought he loses concentration and lets go, falling to his death. This fall was caused by a thought of suicide, perhaps even by an intention to commit suicide, but it was an accident still, caused by a shock rather than carried out deliberately. So intentional actions are not behavior caused by intentions. The intention is a part or an aspect of the act, not a prior event that causes it.