Phenomenology of Spirit, Preface, paragraph 44

The real defect of this cognition, however, affects both cognition itself and its material generally. As to cognition, in the first place we do not see any necessity in the construction. The necessity does not arise from the nature of the theorem, but is bidden; and the injunction to draw just these lines, an infinite number of others being equally possible, is blindly acquiesced in, without our knowing anything further, except having the good faith that this will serve our purpose in producing the proof. At the back end, then, is this expediency manifested, which for this reason is merely external in character, just because it is only at the back end, with the proof, that it is manifest. In the same way, again, the proof takes a direction that begins anywhere we like, without our knowing as yet what relation this beginning has to the result to be brought out. Its progress takes up these determinations and relations and leaves others to one side, without its being directly obvious what necessity there is in it. An external purpose controls this movement.