Plotinos: Complete Works, v. 3 In Chronological Order,...

14. But what about the straight line? Is it not a magnitude? Possibly; but if it be a magnitude, it is a qualified one.391 It is even possible that straightness constitutes a difference of the (very nature of the) line, as line, for straightness refers solely to a line; and besides, we often deduce the differences of "Essence" from its qualities. That a straight line is a quantity added to a difference does not cause its being composed of the line, and of the property of straightness; for, were it thus composed, straightness would be its chief difference.