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found such contradictions and difficulties in every system concerning external objects, and in the idea of matter, which we fancy so clear and determinate, we shall naturally expect still greater difficulties and contradiction in every hypothesis concerning our internal perceptions, and the nature of the mind, which we are apt to imagine so much more obscure, and uncertain. But in this we shou'd deceive ourselves. The intellectual world, tho' involv'd in infinite obscurities, is not perplex'd with any such contradictions, as those we have discover'd in the natural. What is known concerning it, agrees with itself; and what is unknown, we must be contented to leave so.

'Tis true, wou'd we hearken to certain philosophers, they promise to diminish our ignorance; but I am afraid 'tis at the hazard of running us into contradictions, from which the subject is of itself exempted. These philosophers are the curious reasoners concerning the material or immaterial substances, in which they suppose our perceptions to inhere. In order to put a stop to these endless cavils on both sides, I know no better method, than to ask these philosophers in a few words, What they mean by substance and inhesion? And after they have answer'd this question, 'twill then be reasonable, and not till then, to enter seriously into the dispute.

This question we have found impossible to be answer'd with regard to matter and body: But besides that in the case of the mind, it labours under all the same difficulties, 'tis burthen'd with some additional ones, which are peculiar to that subject. As every idea is deriv'd from a precedent impression, had we any idea of the substance of our minds, we must also have an impression of it; which is very