Instinct is untaught ability. - Alexander Bain

The arguments for the two substances - mind and body - have, we believe, entirely lost their validity; they are no longer compatible with ascertained science and clear thinking. One substance with two sets of attributes, two sides (a physical and a mental), a double-faced unity, would appear to comply with all the exigencies of the case.

He that could teach mathematics well, would not be a bad teacher in any of the rest [physics, chemistry, biology, psychology] unless by the accident of total inaptitude for experimental illustration; while the mere experimentalist is likely to fall into the error of missing the essential condition of science as reasoned truth; not to speak of the danger of making the instruction an affair of sensation, glitter, or pyrotechnic show.

The method of arithmetical teaching]] is perhaps the best understood of any of the methods concerned with elementary studies.