Plato does not intend here to distinguish (as many modern writers distinguish) geometry from other sciences, as if geometry were known _à priori_, and other sciences known _à posteriori_ or from experience. He does not suppose that geometrical truths are such that no man can possibly believe the contrary of them; or that they are different in this respect from the truths of any other science. He here maintains that all the sciences lie equally in the untaught mind,[45] but buried, forgotten, and confused: so as to require the skill of the questioner not merely to recall them into consciousness, but to disentangle truth from error. Far from supposing that the untaught mind has a natural tendency to answer correctly geometrical questions, he treats erroneous answers as springing up more naturally than true answers, and as requiring a process of painful exposure before the mind can be put upon the right track. The questioner, without possessing any knowledge himself, (so Plato thinks,) can nevertheless exercise an influence at once stimulating, corrective, and directive. He stimulates the action of the associative process, to call up facts, comparisons, and analogies, bearing on the question: he arrests the respondent on a wrong answer, creating within him a painful sense of ignorance and embarrassment: he directs him by his subsequent questions into the path of right answers. His obstetric aid (to use the simile in Plato's Theætetus), though presupposing the pregnancy of the respondent mind, is indispensable both to forward the childbirth, and to throw away any offspring which may happen to be deformed. In the Theætetus, the main stress is laid on that part of the dialogue which is performed by the questioner: in the Menon, upon the latent competence and large dead stock of an untaught respondent. [Footnote 45: Plato, Menon, p. 85 E. [Greek: ou(=tos ga\r] (the untaught slave) [Greek: poiê/sei peri\ pa/sês geômetri/as tau)ta\ tau=ta, kai\ tô=n a)/llôn mathêma/tôn a(pa/ntôn.]] The mind of the slave questioned by Sokrates is discovered to be pregnant. Though he has received no teaching from any professed geometer, he is nevertheless found competent, when subjected to a skilful interrogatory, to arrive at last, through a series of mistakes, at correct answers, determining certain simple problems of geometry. He knows nothing about geometry: nevertheless there exist in his mind true opinions respecting that which he does not know. These opinions are "called up like a dream" by the interrogatories: which, if repeated and diversified, convert the opinions into knowledge, taken up by the respondent out of himself.[46] The opinions are inherited from an antecedent life and born with him, since they have never been taught to him during this life.