[3rd Ed.]—[The doctrine here propounded, that All Matter is Heavy, has been opposed by Sir William Hamilton of Edinburgh. (Works of Reid, note, p. 853.) This writer is a man of unquestionable acuteness and of very extensive reading; but his acuteness shows itself in barren ontological distinctions, which appear to me to be of the same character as the speculations of the eminent Schoolmen of the most sterile periods of the dark ages. That he should have no conception of progressive or inductive science is not wonderful, when we recollect that he holds, as an important part of his philosophy, that the study of mathematics perverts and obscures the mind. But it may be of some interest to consider his objections to the doctrine here maintained.
He says, 1st, that our reasoning assumes that we must necessarily have it in our power to ascertain the Quantity of Matter; whereas this may be a problem out of the reach of human determination.
To this I reply, that my reasoning does assume that there is a science, or sciences, which make assertions concerning the Quantity of Matter: Mechanics and Chemistry are such sciences. My assertion is, that to make such sciences possible, Quantity of Matter must be proportional to Weight. If my opponent deny that Mechanics and Chemistry can exist as sciences, he may invalidate my proof; but not otherwise.
2. He says that there are two conceivable ways of estimating the Quantity of Matter: by the Space occupied, and by the Weight or Inertia; and that I assume the second measure gratuitously.
To which I reply, that the most elementary steps in Mechanics and in Chemistry contradict the notion that [38] the Quantity of Matter is proportionate to the Space. They proceed necessarily on a distinction between Space and Matter:—between mere Extension and material Substance.
3. He allows that we cannot make the Extension of a body the measure of the Quantity of Matter, because, he says, we do not know if ‘the compressing force’ is such as to produce ‘the closest compression.’ That is, he assumes a compressing force, assumes a closest compression, assumes a peculiar (and very improbable) atomic hypothesis; and all this to supply a reason why we are not to believe the first simple principle of Mechanics and Chemistry.
4. He speaks of ‘a series of apparent fluids (as Light or its vehicle, the Calorific, the Electro-galvanic, and Magnetic agents) which we can neither denude of their character of substance, nor clothe with the attribute of weight.’
To which my reply is, that precisely because I cannot ‘clothe’ these agents with the attribute of Weight, I do ‘denude them of the character of Substance.’ They are not substances, but agencies. These Imponderable Agents are not properly called ‘Imponderable Fluids.’ This I conceive that I have proved; and the proof is not shaken by denying the conclusion without showing any defect in the reasoning.
5. Finally, my critic speaks about ‘a logical canon,’ and about ‘a criterion of truth, subjectively necessary and objectively certain;’ which matters I shall not waste the reader’s time by discussing.]