Use a condom next time you screw my brain
Background: I go to University of Portland, in Portland (surprise) Oregon. Now that we're on the same page, I can relate the following anecdote.

One of my classes this term is Introduction of Philosophy. Every student has to take it, so it's one of "those" classes where the football players and the stoners sit in the back and pass notes while the short Asian kids methodically take down notes and care because it's expected of them. That said, some of the things we discuss are fairly interesting, not to mention bizarre. And bizarre it was today, with our study of Hume and our introduction to metaphysics and ontology.

Hume's an empiricist, which means he thinks that we can only know what we can perceive (or conjecture from our perceptions). The main thrust of the section that we read was that because we cannot directly observe cause and effect, it has no bearing on reality because we cannot (literally cannot, much like a whale cannot fly) understand it. What we usually think of cause and effect phenomena, when boiled down to its component parts, is nothing more than a set of actions that follow one another, but there is nothing labeled "cause" that we can see.

If he's right, it basically tosses out all of science, since the scientific method is immutably based on cause and effect.