The standard view among philosophers is that an arguer’s hypocrisy(understood as failure to practice what one preaches)has no bearing on either the merits of his or her argument or the acceptability of the argument’s conclusion.I challenge this view.Using the case of Peter Singer,who has famously argued for a moral obligation to relieve famine,but who does not,by his own admission,live in accordance with the standard he espouses,I explain why(and how)an arguer’s hypocrisy matters.If I am correct,then the standard view of the relation between arguer and argument must be revised.