In objecting against the thirteenth and sixteenth article, I observe that you bewray together, both the greatest ignorance and the greatest malice; and it is well, for they are suitable to one another, and fit for one and the same man. In the thirteenth article my proposition is this: _If there be three magnitudes that have proportion one to another, the proportions of the first to the second, and of the second to the third, taken together_ (as one proportion), _are equal to the proportion of the first to the third_. This demonstrated, there is taken away one of those moles which Sir Henry Savile complaineth of in the body of geometry. Let us see now what you say, both against the enunciation and against the demonstration. Against the enunciation you object, _that other men would say_ (not the proportions of the first to the second, and of the second to the third, taken together, &c. but) _the proportion which is compounded of the proportion of the first to the second, and of the second to the third_, &c. Is not the compounding of any two things whatsoever the finding of the sum of them both, or the taking of them together as one total? This is that absurdity of which Mersennus, in the general preface to his _Cogitata Physico-Mathematica_, hath convinced Clavius, who, at the end of Euclid’s ninth Element, denieth the composition of proportion to be a composition of parts to make a total; which, therefore, he denied, because he did not observe, that the addition of a proportion of defect to a proportion of excess, was a subtraction of magnitude; and because he understood not that to say, composition is not the making a whole of parts, was contradiction; which all but too learned men would as soon as they heard abhor. Therefore, in saying that other men would not speak in that manner, you say in effect they would speak absurdly. You do well to mark what other geometricians say; but you would do better if you could by your own meditation upon the things themselves, examine the truth of what they say. But you have no mind, you say, to contend about the phrase. Let us see, therefore, what it is you contend about.