TOTA, ET TOTALITER; which is the very definition of penetration. But
penetration is impossible: Mathematical points are of consequence equally
impossible.

I answer this objection by substituting a juster idea of penetration.
Suppose two bodies containing no void within their circumference, to
approach each other, and to unite in such a manner that the body, which
results from their union, is no more extended than either of them; it is
this we must mean when we talk of penetration. But it is evident this
penetration is nothing but the annihilation of one of these bodies, and
the preservation of the other, without our being able to distinguish
particularly which is preserved and which annihilated. Before the
approach we have the idea of two bodies. After it we have the idea only
of one. It is impossible for the mind to preserve any notion of difference
betwixt two bodies of the same nature existing in the same place at the
same time.

Taking then penetration in this sense, for the annihilation of one body
upon its approach to another, I ask any one, if he sees a necessity, that
a coloured or tangible point should be annihilated upon the approach of
another coloured or tangible point? On the contrary, does he not
evidently perceive, that from the union of these points there results an
object, which is compounded and divisible, and may be distinguished into
two parts, of which each preserves its existence distinct and separate,
notwithstanding its contiguity to the other? Let him aid his fancy by
conceiving these points to be of different colours, the better to prevent
their coalition and confusion. A blue and a red point may surely lie
contiguous without any penetration or annihilation. For if they cannot,
what possibly can become of them? Whether shall the red or the blue be
annihilated? Or if these colours unite into one, what new colour will