2. The proof of the non-existence of the primary qualities or of matter altogether, as inconceivable by the mind, goes upon the supposition that what is different cannot be the same. ‘An idea,’ says Berkeley, ‘can be like nothing but an idea, a perception like nothing but a perception.’ But it might be proved in this manner that a print cannot resemble a picture, because that which has colour cannot be represented by any thing without colour. That as far as our ideas are perceptions they do not resemble any thing in matter is true, but no one ever supposed that in this respect there was any resemblance between them, or that matter thought. That they cannot be alike in any thing does not seem to me proved by this mode of reasoning: for that our ideas of things are not mere perceptions is evident from this, that they are different among themselves, that is, have other distinguishing qualities besides being perceived. 3. Berkeley’s argument against the existence of matter not merely as the object or archetype, but as the cause of our sensations, is founded on the notion that we have a right to reject every general conclusion in which there is the least flaw or difficulty. Common sense is brought to the bar, like an old offender, and condemned upon the slightest shadow of evidence. If the vulgar system is vulnerable in any part, it is taken for granted that it ought to be discarded, to make room for a perfectly rational and philosophical account, the sufficiency of the understanding being never once doubted. But all this severe logic and scrutiny into the perfect connexion of our ideas vanishes, when the author comes to explain the cause of our external impressions, or to find a substitute for matter. This, he says, is God or an all-powerful spirit, and yet he affirms that we have no more idea of spirit than of matter, and consequently the one ought upon this theory to pass for a nonentity as much as the other. ‘We perceive a continual succession of ideas, some are anew excited, others are changed or totally disappear. There is therefore some cause of those ideas, whereon they depend, and which produces and changes them. That this cause cannot be any quality or idea or combination of ideas, is clear from what has been said. It must therefore be a substance, but it has been shewn that there is no corporeal or material substance. It remains therefore that the cause of ideas is an incorporeal active substance or spirit.