From Pensées 40:
If we wished to prove the examples which we take to prove other things, we should have to take those other things to be examples; for, as we always believe the difficulty is in what we wish to prove, we find the examples clearer and a help to demonstration.
Thus, when we wish to demonstrate a general theorem, we must give the rule as applied to a particular case; but if we wish to demonstrate a particular case, we must begin with the general rule. For we always find the thing obscure which we wish to prove and that clear which we use for the proof; for, when a thing is put forward to be proved, we first fill ourselves with the imagination that it is, therefore, obscure and, on the contrary, that what is to prove it is clear, and so we understand it easily.
Obscurity is the inherent problem with systems of thought that begin with man (particulars) and not with God (universal). That is why materialism, ethical objectivism, and moral relativism all end up in an incoherent mess when followed to their conclusion.