(conjunctive) Consequently, by or in consequence of that or this cause; referring to something previously stated. / (conjunctive, archaic) for that; for it (in reference to a previous statement)

(now chiefly in law) For that; in return for that.

Obsolete spelling of therefore

(philosophy) I am able to think, therefore I exist. A philosophical proof of existence based on the fact that someone capable of any form of thought necessarily exists.