CONTINUITY, LAW OF. A principle first formulated by Leibnitz (q.v.), which is expressed in the Latin sentence, Nature non Tacit saltum ("Nature does not make sudden leaps"). it is opposed to the principle of discreteness, which asserts that all differences are hard and fixed, and that differences of kind are not differences of degree. Of late the significance of the law of continuity is coining more and more to be recog nized. Indeed, it is the fundamental presupposi tion of all evolutionary thought, which maintains that all the differences of organic species and genera are differences appearing here and there in a continuum of variation, and that they get their discrete elmracter from the disappearance of intergradient forms. The law of continuity may be illustrated in many ways. The solar spectrum, for instance, presents us with a series of colors which blend into each other in such a way that it is impossible to say where one color ends and another begins. Within this series we see many recognizably distinct colors; but this really means that red and blue are so different that a normal eye cannot confuse them. It does
not mean that they are so different that no con ceivable difference in degree can account for the difference in kind. In fact, it takes only a glance at the spectrum to see that the difference in kind is mediated by differences in degree, and that these latter are not abrupt and intermittent, but con tinuous and unbroken. By abstracting from the intervening colors and shades we can represent any detectable differences to ourselves as discrete, but this appearance of discreteness comes from failure to attend to the mediating shades. It is, however, to be observed that the continuity of the difference does not in the least prejudice the fact of difference. This truth can be stated in the following paradox: The colors and shades that separate two given colors in a spectrum also unite them. Generalizing this, we get the law that all intervenients while uniting separate, and while separating unite, the extremes between which they lie. See IDENTITY; and for the con tinuity of the states of aggregation of chemical substances, CRITICAL POINT.