law which is true of the first class of commodities only to be true of all classes of them. 2. _Wages._ Having concluded by the vicious argument now explained that all value is the creation of the personal labour of the workman--is but the registered duration of exertion of his labouring powers--Marx next proceeds to show that, as things at present exist, the value of these labouring powers themselves is fixed not by what they create but by what is necessary to create or at least renovate them. The rate of wages, economists have taught, is determined by the cost of the production of labouring powers, and that is identical with the cost of maintaining the labourer in working vigour. Marx accepts the usual explanations of the elasticity of this standard of cost of subsistence. It includes, of course, the maintenance of the labourer's family as well as his own, because he will die some day, and the permanent reproduction of powers of labour requires the birth of fresh hands to succeed him. It must also cover the expenses of training and apprenticeship, and Marx would probably agree to add, though he does not actually do so, a superannuation allowance for old age. It contains, too, a variable historical element, differs with climate and country, and is, in fact, just the customary standard of living among free labourers of the time and place. The value of a commodity is the time of labour required to deliver it in _normal goodness_, and to preserve the powers of labour in normal goodness a definite quantity of provisions and comforts is necessary according to time, country, and customs. The part of the labouring day required to produce this definite quantity of provisions and comforts for the use of the day may be called the _necessary time of labour_--the time during which the workman produces what is necessary for keeping him in existence--and the value created in this season may be called _necessary value_. But the workman's physical powers may hold on labouring longer than this, and the rest of his working day may accordingly be called _surplus time of labour_, and the value created in it _surplus value_. This surplus value may be created or increased in two ways: either by reducing or cheapening the labourer's subsistence, _i.e._, by shortening the term of necessary labour; or by prolonging the length of the working day, _i.e._, by increasing the term of surplus labour. There are limits indeed within which this kind of action must stop. The quantity of means of life cannot be reduced below the minimum that is physically indispensable to sustain the labourer for the day, and the term of labour cannot be stretched beyond the labourer's capacity of physical endurance. But within these limits may be played an important _rôle_, and the secret of surplus value lies in the simple plan of giving the labourer as little as he is able to live on, and working him as long as he is able to stand. A labourer works 12 hours a