In the next place, you reprehend briefly this _corollary, that two planes cannot enclose a solid_. I should, indeed, have added, _with the base on whose extremes they insist_: but this is not a fault to be ashamed of; for any man, by his own understanding, might have mended my expression without departing from my meaning. But from your doctrine, _that a superficies has no thickness_, it is impossible to include a solid, with any number of planes whatsoever, unless you say that solid is included which nothing at all includes. At the third article, where I say _of crooked lines, some are everywhere crooked, and some have parts not crooked_. You ask me what crooked line has parts not crooked; and I answer, it is that line which with a straight line makes a rectilineal triangle. But this, you say, cannot stand with what I said before, namely, that a straight and crooked line cannot be coincident; which is true, nor is there any contradiction; for that part of a crooked line which is straight, may with a straight line be coincident. To the fourth article, where I define _the centre of a circle to be that point of the radius, which in the description of the circle is unmoved_; you object as a contradiction, that I had before defined a point to be the body which is moved in the description of a line: foolishly, as I have already shown at your objection to Chap. VIII. art. 12. But at the sixth article, where I say, that _crooked and incongruous lines touch one another but in one point_, you make a cavil from this, that _a circle may touch a parabola in two points_. Tell me truly, did you read and understand these words that followed? “_A crooked line cannot be congruent with a straight line; because if it could, one and the same line should be both straight and crooked._” If you did, you could not but understand the sense of my words to be this: _when two crooked lines which are incongruous, or a crooked and a straight line touch one another, the contact is not in a line, but only in one point_; and then your instance of a circle and a parabola was a wilful cavil, not befitting a doctor. If you either read them not, or understood them not, it is your own fault. In the rest that followeth upon this article, with your diagram, there is nothing against me, nor anything of use, novelty, subtlety, or learning.