 Now as the angle XYZ is increased, the point B describes the curve AB, which is a circle; while the intersections of the other rulers, namely, the points D, F, H describe the other curves, AD, AF, AH, of which the latter are more complex than the first and this more complex than the circle. Nevertheless I see no reason why the description of the first cannot be conceived as clearly and distinctly as that of the circle, or at least as that of the conic sections; or why that of the second, third, or any other that can be thus described, cannot be as clearly conceived of as the first: and therefore I see no reason why they should not be used in the same way in the solution of geometric problems (G,  44–47).[7]