Why do we accept the maxim 'whatever begins to exist must have a cause'?, and How does the psychological process of probable reasoning work? Addressing the first question, Hume argues that the maxim is not founded on intuition or demonstration (contending that we can at least conceive of objects beginning to exist without a cause), and then rebuts four alleged demonstrations of the maxim. He concludes that our acceptance of this maxim must be somehow drawn "from observation and experience", and thus turns to the second question. Sections 4–8 Hume develops a detailed three-stage psychological account of how probable reasoning works (i.e., how "the judgement" operates). First, our senses or memory must present us with some object: our confidence in this perception (our "assent") is simply a matter of its force and vivacity. Second, we must make an inference, moving from our perception of this object to an idea of another object: since the two objects are perfectly distinct from each other, this inference must draw on past experience of the two objects being observed together again and again. (This "constant conjunction" is promptly filed alongside contiguity and priority, in Hume's still-developing account of our idea of causation.) But what exactly is the process by which we draw on past experience and make an inference from the present object to the other object? Here the famous "problem of induction" arises. Hume argues that this all-important inference cannot be accounted for by any process of reasoning: neither demonstrative reasoning nor probable reasoning. Not demonstrative reasoning: it cannot be demonstrated that the future will resemble the past, for "[w]e can at least conceive a change in the course of nature", in which the future significantly differs from the past. And not probable reasoning: that kind of reasoning itself draws on past experience, which means it presupposes that the future will resemble the past. In other words, in explaining how we draw on past experience to make causal inferences, we cannot appeal to a kind of reasoning that itself draws on past experience—that would be a vicious circle that gets us nowhere. The inference is not based on reasoning, Hume concludes, but on the association of ideas: our innate psychological tendency to move along the three "natural relations". Recall that one of the three is causation: thus when two objects are constantly conjoined in our experience, observing the one naturally leads us to