If we carry our inquiry beyond the appearances of objects to the senses, I am afraid, that most of our conclusions will be full of scepticism and uncertainty. Thus, if it be asked, whether or not the invisible and intangible distance be always full of _body_, or of something that by an improvement of our organs might become visible or tangible, I must acknowledge, that I find no very decisive arguments on either side: though I am inclined to the contrary opinion, as being more suitable to vulgar and popular notions. If _the Newtonian_ philosophy be rightly understood, it will be found to mean no more. A vacuum is asserted; that is, bodies are said to be placed after such a manner as to receive bodies betwixt them, without impulsion or penetration. The real nature of this position of bodies is unknown. We are only acquainted with its effects on the senses, and its power of receiving body. Nothing is more suitable to that philosophy, than a modest scepticism to a certain degree, and a fair confession of ignorance in subjects that exceed all human capacity. SECTION VI. OF THE IDEA OF EXISTENCE, AND OF EXTERNAL EXISTENCE. It may not be amiss, before we leave this subject, to explain the ideas of _existence_ and of _external existence_; which have their difficulties, as well as the ideas of space and time. By this means we shall be the better prepared for the examination of knowledge and probability, when we understand perfectly all those particular ideas, which may enter into our reasoning. There is no impression nor idea of any kind, of which we have any consciousness or memory, that is not conceived as existent; and 'tis evident that, from this consciousness, the most perfect idea and assurance of _being_ is derived. From hence we may form a dilemma, the most clear and conclusive that can be imagined, viz. that since we never remember any idea or impression without attributing existence to it, the idea of existence must either be derived from a distinct impression, conjoined with every perception or object of our thought, or must be the very same with the idea of the perception or object. As this dilemma is an evident consequence of the principle, that every idea arises from a similar impression, so our decision betwixt the propositions of the dilemma is no more doubtful. So far from there being any distinct impression attending every impression and every idea, that I do not think there are any two distinct impressions which are inseparably conjoined. Though certain sensations may at one time be united, we quickly find they admit of a separation, and may be presented apart. And thus, though every impression and idea we remember be considered as existent, the idea of existence is not derived from any particular impression.