David Hume/Could outconsume/Jacques Derrida (1930 - 2004), noted French philosopher

I cannot forbear adding to these reasonings an observation, which may, perhaps, be found of some importance. In every system of morality, which I have hitherto met with, I have always remark’d, that the author proceeds for some time in the ordinary way of reasoning, and establishes the being of a God, or makes observations concerning human affairs; when of a sudden I am surpriz’d to find, that instead of the usual copulations of propositions, is, and is not, I meet with no proposition that is not connected with an ought, or an ought not. This change is imperceptible; but is, however, of the last consequence. For as this ought, or ought not, expresses some new relation or affirmation, ‘tis necessary that it shou’d be observ’d and explain’d; and at the same time that a reason should be given, for what seems altogether inconceivable, how this new relation can be a deduction from others, which are entirely different from it. But as authors do not commonly use this precaution, I shall presume to recommend it to the readers; and am persuaded, that this small attention wou’d subvert all the vulgar systems of morality, and let us see, that the distinction of vice and virtue is not founded merely on the relations of objects, nor is perceiv’d by reason.

David Hume -- Treatise of Human Nature

This, for my money, is probably the most important paragraph in all of philosophy. Shorter version: You can't deduce statements of value from statements of fact. Which, I just now found out, is known as the is-ought problem. And actually, if you understand that, and couple that with what deconstruction tells us, namely that all statements of fact are dependent upon (or even are) statements of value, you understand the idea of language as a closed system of deferred meaning. And then you're really ready to party. Right. Enough theory for today. I'm going to go write.