‘It is agreed on all hands,’ says this author, ‘that the quantities or modes of things do never really exist in each of them, apart by itself, and separated from all others, but are mixed, as it were, and blended together, several in the same object. But we are told the mind being able to consider each quality singly, or abstracted from those other qualities with which it is united, does by that means frame to itself abstract ideas. For example, there is perceived by sight, an object, extended, coloured, and moved. This mixed idea the mind resolving into its simple constituent parts, and viewing each by itself exclusive of the rest, does frame the abstract ideas of extension, colour, and motion. Not that it is possible for colour or motion to exist without extension, but only that the mind can frame to itself by abstraction the idea of colour, exclusive of extension, and of motion exclusive both of colour and extension. Again, the mind having observed that in the particular extensions perceived by sense, there is something common and alike in all, and some other things peculiar, as this or that figure, or magnitude, which distinguish them one from another, it considers apart, or singles out by itself that which is most common, making thereof a most abstract idea of extension, line, surface, or solid, nor has any figure or magnitude, but is an idea prescinded from all these. So likewise the mind by leaving out of the particular colours perceived by sense, that which distinguishes them one from another, and retaining that which only is common to all, makes an idea of colour in abstract, which is neither red, nor blue, not white, &c. And in like manner by considering motion abstractedly, not only the body moved, but likewise from the figure it describes, and all particular directions and velocities, the abstract idea of motion is framed, which equally corresponds to all particular motions whatsoever that may be perceived by sense.