SHARP POINT

"The course notes contained a detail which at first reading had escaped me, namely, that the so tender and delicate zinc, so yielding to acid which gulps it down in a single mouthful behaves, however, in a very different fashion when it is very pure: then it obstinately resists attack. One could draw from this two conflicting philosophical conclusions: the praise of purity, which protects from evil like a coat of mail; the praise of impurity, which gives rise to changes, in other words, to life."

Primo Levi, "Zinc" from The Periodic Table