Two circumstances operate to keep the requirement of consideration alive in our law of simple contract. One is the professional feeling that the common law is the legal order of nature, that its doctrines in an idealized form are natural law and that its actual rules are declaratory of natural law. This mode of thinking is to be found in all professions and is a result of habitual application of the rules of an art until they are taken for granted. In law it is fortified by the theory of natural law which has governed in our elementary books since Blackstone, was taught to all lawyers until the present century, and is assumed in much of our judicial decision. Later it was strengthened by the theories of the historical school which ruled in our law schools in the last quarter of the nineteenth century and taught us to think that growth must inevitably follow lines which might be discovered in the Year Books. These things co-operated with the temper of the last century and the instinctive aversion of the lawyer to change, lest in some unperceived way a door be opened to magisterial caprice or to the personal equation of the judge. Thus some thought of consideration, whatever it was, as inherent in the very idea of enforceable promises. Others assumed that it was a historically developed principle by which the future evolution of the law of contracts must be governed. Many others simply thought that it was dangerous to talk of change. And yet change has gone on rapidly, if subconsciously, until the present confused mass of unsystematized and unsystematizable rules has resulted. The second circumstance operating to keep alive the requirement of consideration is a more legitimate factor.