The other basic principle affecting all questions of labor law is that of freedom of trade or labor, correlative to the principle of freedom of contract as to property right, and, indeed, embodying that notion also. That is to say (perhaps I should say, to repeat) that an Englishman, an American, has a right to labor where and for whom and at what he will, and freely to make contract for such labor, and freely to exercise all trades, and not to be combined against by others, or competed with by a monopoly favored by the state. These last two clauses, of course, belong to our next chapter. This right of contract is not peculiar to the English law, as is the right not to be compelled to personal service, and is much better understood; though it is still earnestly argued by many advocates of union labor that there is no real freedom of contract, or, at least, equality of contract, between the employer and the employee; that therefore "collective bargaining" should be allowed, and that therefore, and furthermore, the wiser or the better organized should be permitted to combine to control the contract or the labor of the individual. But if we hold thoroughly these two principles before our mind we shall have the key to the understanding of our labor legislation; and if we add to that the third principle against conspiracy, we shall have the key to our more complicated legislation against trusts and blacklists and boycotts, and to an understanding of the more difficult questions, affecting labor in combination and the regulation of labor unions. That there has been a vast deal of interference, or attempted interference, with these principles in modern American legislation goes without saying. The motive or force behind such legislation has pretty clearly two sources: First, the behest or desire of the "Labor interest" or organized labor, the trades-unions themselves; and when we analyze these and their constituents we shall find that it really means only mechanical or industrial labor, not farm or agricultural labor (which is still in numbers the greatest body of labor in the United States), nor, as yet, domestic service labor, nor what the census calls "personal service," which is probably next in numerical importance, nor clerks; it is a comparatively small class in numbers, this class of skilled mechanical or manufacturing labor, that has brought about this immense mass of legislation of our modern States aimed at improving their own labor conditions; and which therefore, necessarily perhaps, interferes with personal liberty as to the labor contract, or, at least, seeks to regulate it.