A writer whose work on contracts has had great currency,4 enumerates as requisite for the formation of contract the legality of the object which the contract proposes to effect, and this statement has often been copied or the statement made that illegal contracts are void. It would seem that the legality of the object for which a contract was formed is of no greater importance than the legality of the consideration for which the promise was given. Illegality in either respect will generally preclude enforcement of the contract, but the subsequent discussion of the subject of illegality 5 will indicate that by no means all illegal agreements are void or, so far as one party to them is concerned, even unenforceable. The effect of illegality undoubtedly often is to make the contract unenforceable by both parties, and almost always to make it unenforceable by one party. But as illegal contracts are not infrequently enforceable by one party to them, and sometimes by both parties, it is obvious that legality is not one of the absolute requisites for the formation of contracts, though doubtless by statute a forbidden agreement may be declared absolutely void.