Da Vinci on human worth

Here's what Leonardo Da Vinci wrote on the back of one of his drawings. Notebooks p. 1140. The link has his notebooks transcribed and syndicated by RSS, if you're looking for a genius to add to your reader.

And you, O Man, who will discern in this work of mine the wonderful works of Nature, if you think it would be a criminal thing to destroy it, reflect how much more criminal it is to take the life of  a man; and if this, his external form, appears to thee marvellously constructed, remember that it is nothing as compared with the soul  that dwells in that structure; for that indeed, be it what it may, is a thing divine. Leave it then to dwell in His work at His good will and pleasure, and let not your rage or malice destroy a life--for indeed, he who does not value it, does not himself deserve it.

 I'd put the same argument to someone who kills to steal great art, to someone who ignores his family responsibilities while writing a blog post, or to someone who tells his mistress that the Mexican Revolution failed and it's not his fault.