Hume is indeed sceptical about the power of reason to determine what we believe. But he is not sceptical, for example, about whether the sun will rise tomorrow. He just has the calm understanding that our confidence in uniformities in nature, such as this one, is not the result of logic or of any exercise of pure rationality. It is just the way our minds happen to work—as indeed, do those of other animals.
Similarly when it comes to understanding the springs of action, Hume again dethrones reason, arguing that nothing that reason could discover would motivate us without engaging an inclination or ‘passion’. He entirely overturns the Platonic model of the soul in which reason is the charioteer, controlling and steering the unruly horses of desire. ‘Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them’. We can correct mistakes about the world in which we act, and choose more efficient means to gain our ends. We may even be able to persuade ourselves and each other to alter our courses, for better or worse. But we can only do this by mobilizing other considerations we care about. These concerns, or in other words the directions of our desires, are themselves a bare gift of nature, again. Hume excelled in adding detail to this: his account of the evolution of what he called the ‘artificial’ virtues—respect for such things as reciprocity, institutions of justice, social conventions, law or government—is the grandfather of all later decision-theoretic and game-theoretic approaches to the evolution of cooperation. But it took over two centuries before this would be recognized. Only recently has Hume’s naturalism become the gold standard for everyone at the cutting edge of contemporary investigation, whether in philosophy, psychology, evolutionary psychology, anthropology, or neurophysiology.
Hume's Wikipedia page.