2. The metaphysical argument, in the broadest form, is put thus: Wherever there are objects of sense, sentient beings must also exist. Or take a particular example: It is held bj the author of the "Natural History of the Vestiges of Creation," that whereever light exists, there must be eyes to perceive it. Now, in one point of view, this is a mere circular argument; for if light be so defined, that it necessarily implies the exercise of vision, then, undoubtedly, the existence of light implies an eye. If it be maintained that light does not consist merely in the undulations of an ethereal medium, but in the sensation which that vibration produces by acting on the optic nerve, then, unquestionably, there can be no light where there is no sensation. But, then, all that the argument amounts to is this, that where there is no eye, there can be no sensation of light; and in reference to the planets, that if there is a sensation of light, then there must be an eye through which that sensation is produced. But that is the very point to be established. We know that the vibrations which cause the sensation of light reach the planets; but the question is. Is there an eye to receive these vibrations, and through which the sensation of light may be produced? We can quite readily conceive the vibrations to exist without the eye to receive them. It may be argued that, in all probability, the vibrations would not be sent to these bodies, unless there were eyes to receive them; but this is taking up new
