Substance. / \ / \ Corporeal Incorporeal \ \ Body / \ / \ Animate Inanimate \ \ Living Being / \ / \ Sensible Insensible \ \ Animal / \ / \ Rational Irrational \ \ Man / | \ / | \ / | \ Socrates Plato Other Men This kind of division is not altogether satisfactory as the negative side is too indefinite. On the other hand, if both subdivisions are made positive then there is danger of making the opposing terms contrary rather than contradictory. This, of course, would be a serious logical fallacy, as contrary terms admit of middle ground while contradictory terms give no choice, it is either the one or the other. The use of dichotomy becomes evident in situations where new and unexpected discoveries may be made. Without disturbing the classification the new species may be appended to the negative side of the division. The following illustrates: Vertebrates ┌───────┴──────────┐ │ │ Leptocardians Not-leptocardians ┌──────────┴───┐ │ │ Fish Not-fish ┌───────────┴────┐ │ │ Amphibians Not-amphibians ┌──────────────┴────┐ │ │ Reptiles Not-reptiles ┌────────────────┴───┐ │ │ Birds Not-birds ┌──────────────────┴──┐ │ │ Mammals Not-mammals │ _The New Species_ =6. CLASSIFICATION――COMPARED WITH DIVISION.= _Classification is the process of grouping notions according to their resemblances or connections._