There is another Sceptical Topic of a like Nature, deriv'd from the most profound Philosophy; which might merit our Attention were it requisite to dive so deep, in order to discover Arguments and Reasonings, that can serve so little any serious Purpose or Intention. 'Tis universally allow'd by modern Enquirers, that all the sensible Qualities of Objects, such as hard, soft, hot, cold, white, black, &c. are merely secondary, and exist not in the Objects themselves, but are Perceptions in the Mind, without any external Archetype or Model, which they represent. If this be allow'd, with regard to secondary Qualities, it must also follow with regard to the suppos'd primary Qualities of Extension and Solidity; nor can the latter be any more entitled to that Denomination than the former. The Idea of Extension is entirely acquir'd from the Senses of Sight and Feeling; and if all the Qualities, perceiv'd by the Senses, be in the Mind, not in the Object, the same Conclusion must reach the Idea of Extension, which is wholly dependent on the sensible Ideas or the Ideas of secondary Qualities. Nothing can save us from this Conclusion, but the asserting, that the Ideas of those primary Qualities are attain'd by Abstraction; which, if we examine accurately, we shall find to be unintelligible, and even absurd. An Extension, that is neither tangible nor visible, cannot possibly be conceiv'd: and a tangible or visible Extension, which is neither hardnor
