The ultimate question that Hume seems to be seeking an answer to is that of why is that we believe what we believe. For most of us the answer is grounded in our own personal experiences and can in no way be justified by a common or worldly assumption. Our pasts, according to Hume, are reliant on some truths which we have justified according to reason, but in being a skeptic reason is hardly a solution for anything concerning our past, present or future. Our reasoning according to causality is slightly inhibited in that Hume suggests that it is not that we are not able to know anything about future events based on past experiences, but rather that we are just not rationally justified in believing those things that we do. We can most certainly make inferences based on causal reasoning, but these inferences have no proofs.
Insofar as empiricism questions all that we experience a posteriori there is no other outcome but skepticism. We must doubt all the senses as they can fool us and often times they do. Nonetheless there can be no doubt to the notion that there is some power that draws us to be skeptics or that leads us to be rational. We are both at the same time, and this, I believe, is what creates the natural balance of the universe and our lives. There is some form of harmonic coexistence within us that allows for such uncertainties to be present in our lives, but at the same time that allows us to have undeniable, justifiable [and sometimes unjustifiable] truths to which we hold onto for the explanation of things such as our very own existence. Everything we think we know is upheld only by what Descartes has taught us, the cogito. Individualistically, we have reason and we believe what we choose to believe.
On the basis o ...