8. And why.
Nor are we to wonder that powers make a great part of our complex ideas of substances; since their
secondary qualities are those which in most of them serve principally to distinguish substances one from another,
and commonly make a considerable part of the complex idea of the several sorts of them. For, our senses failing
us in the discovery of the bulk, texture, and figure of the minute parts of bodies, on which their real constitutions
and differences depend, we are fain to make use of their secondary qualities as the characteristical notes and
marks whereby to frame ideas of them in our minds, and distinguish them one from another: all which secondary
qualities, as has been shown, are nothing but bare powers. For the colour and taste of opium are, as well as its
soporific or anodyne virtues, mere powers, depending on its primary qualities, whereby it is fitted to produce
different operations on different parts of our bodies.
