To make any contract binding, obligatory, and effectual for conveying and transferring rights of property, these three conditions only are essential, _viz._, 1. That it be entered into by parties, who are mentally competent to make reasonable contracts. 2. That the contract be a purely voluntary one: that is, that it be entered into without either force or fraud on either side. 3. That the right of property, which the contract purports to convey, be such an one as is naturally capable of being conveyed, or transferred, by one man to another. Subject to these conditions, all contracts whatsoever, for conveying rights of property--that is, for buying and selling, borrowing and lending, giving and receiving property--are naturally obligatory, and bind such rights of property as they purport to convey. Subject to these conditions, all contracts, for the conveyance of rights of property, are recognized as valid, all over the world, by both civilized and savage man, except in those particular cases where governments arbitrarily and tyrannically prohibit, alter, or invalidate them. This _natural_ "obligation of contracts" must necessarily be presumed to be the one, and the only one, which the constitution forbids to be impaired, by any State law whatever, if we are to presume that the constitution was intended for the maintenance of justice, or men's natural rights. On the other hand, if the constitution be presumed not to protect this _natural_ "obligation of contracts," we know not _what_ other "obligation" it did intend to protect. It mentions no other, describes no other, gives us no hint of any other; and nobody can give us the least information as to what other "obligation of contracts" was intended. It could not have been any "obligation" which the _State_ lawmakers might arbitrarily create, and annex to _all_ contracts; for this is what no lawmakers have ever attempted to do. And it would be the height of absurdity to suppose they ever will invent any _one_ "obligation," and attach it to _all_ contracts. They have only attempted either to annul, or impair, the natural "obligation" of _particular_ contracts; or, _in particular cases_, to substitute other "obligations" of their own invention. And this is the most they will ever attempt to do. SECTION XIX. Assuming it now to be proved that the "obligation of contracts," which the States are forbidden to "impair," is the _natural_ "obligation"; and that, _constitutionally speaking_, this provision secures to all the people of the United States the right to enter into, and have the benefit of, all contracts whatsoever, that have that _one natural_ "obligation," let us look at some of the more important of those State laws that have either impaired that obligation or prohibited the exercise of that right. 1. That law, in all the States, by which any, or all, the contracts of persons, under twenty-one years of age, are either invalidated, or forbidden to be entered into.