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FORE:We cannot, then, agree with those critics who attribute to Aristotle a recognition of such things as ��laws of nature,�� in the sense of uniform co-existences and sequences.279 Such an idea implies a certain balance and equality between subject and predicate which he would never have admitted. It would, in his own language, be making relation, instead of substance, the leading category. It must be remembered also that he did not acknowledge the existence of those constant conjunctions in Nature which we call laws. He did not admit that all matter was heavy, or that fluidity implied the presence of heat. The possession of constant properties, or rather of a single constant property��circular rotation��is reserved for the aether. Nor is this a common property of different and indefinitely multipliable phenomena; it characterises a single body, measurable in extent and unique in kind. Moreover,386 we have something better than indirect evidence on this point; we have the plain statement of Aristotle himself, that all science depends on first principles, about which it is impossible to be mistaken, precisely because they are universal abstractions not presented to the mind by any combination,280��a view quite inconsistent with the priority now given to general laws.Let the reader compare a hammer with a wheel and axle, inclined plane, screw, or lever, as an agent for concentrating and applying power, noting the principles of its action first, and then considering its universal use, and he will conclude that, if there is a mechanical device that comprehends distinct principles, that device is the common hammer. It seems, indeed, to be one of those provisions to meet a human necessity, and without which mechanical industry could not be carried on. In the manipulation of nearly every kind of material, the hammer is continually necessary in order to exert a force beyond what the hands may do, unaided by mechanism to multiply their force. A carpenter in driving a spike requires a force of from one to two tons; a blacksmith requires a force of from five pounds to five tons to meet the requirements of his work; a stonemason applies a force of from one hundred to one thousand pounds in driving the edge of his tools; chipping, calking, in fact nearly all mechanical operations, consist more or less in blows, such blows being the application of accumulated force expended throughout a limited distance. Donec sit amet ligula enim. Duis vel condimentum massa.