In Shakespeare's day, Petruchio describes Grumio as "a senseless villain" (The Taming of the Shrew, I.ii.36). But usually, at that time, the word was used with the older, literal meaning, "lacking human sensation, incapable of feeling", and thus applied chiefly to objects such as stones, trees and the wind. In Cymbeline, Innogen describes Posthumus' handkerchief as "senseless linen" (I.iv.7) and in the same play Pisanio calls a letter a "senseless bauble" (III.ii.20). Referring to people, the meaning is "insensible, oblivious". Timon's steward bemoans the way his master spends money "senseless of expense" (Timon of Athens, II.ii.1). There is a play on the two meanings when in Julius Caesar Marullus harangues the people: "You blocks, you stones, you worse than senseless things!" (I.i.35). They are evidently not only incapable of feeling anything, but also stupid.
David Crystal is author, with Ben Crystal, of Shakespeare's Words, published by Penguin