causes to other men; another from the worthlessness of a liar and the violation of his own self-respect, what is proved in the former argument is a duty of benevolence, not of veracity, that is to say, not the duty which required to be proved, but a different one. Now, if, in giving a variety of proof for one and the same theorem, we flatter ourselves that the multitude of reasons will compensate the lack of weight in each taken separately, this is a very unphilosophical resource, since it betrays trickery and dishonesty; for several insufficient proofs placed beside one another do not produce certainty, nor even probability. They should advance as reason and consequence in a series, up to the sufficient reason, and it is only in this way that they can have the force of proof. Yet the former is the usual device of the rhetorician.