[2] By a _vera causa_, in the logic of science, is meant a state of things known to exist in some cases and supposed to exist in other cases, because it would account for observed phenomena. [3] Wiedemann, _Annalen_, 1887-1889. [4] See Maxwell on Spherical Harmonics, in his _Electricity and Magnetism_. [5] The word _system_ has three peculiar meanings in mathematics. (_A._) It means an orderly exposition of the truths of astronomy, and hence a theory of the motions of the stars; as the Ptolemaic _system_, the Copernican _system_. This is much like the sense in which we speak of the Calvinistic _system_ of theology, the Kantian _system_ of philosophy, etc. (_B._) It means the aggregate of the planets considered as all moving in somewhat the same way, as the solar _system_; and hence any aggregate of particles moving under mutual forces. (_C._) It means a number of forces acting simultaneously upon a number of particles. [6] But, in fact, an inspection of these curves is sufficient to show that they are of a higher degree than the third. For they have the line _V_ = 0, or some line _V_ a constant for an asymptote, while for small values of _P_, the values of (_d_²)_P_/(_dV_)² are positive. [7] Anticipated by Clausius as long ago as 1857; and by Williamson in 1851. [8] “Physiologically, ... accommodation means the breaking up of a habit.... Psychologically, it means reviving consciousness.” Baldwin, _Psychology_, Part III ch. i., § 5. THE FUTURE OF THOUGHT IN AMERICA. History teaches us the nature of the degenerative and destructive agencies in national life. These are of various kinds, but they may be generally included under the heads of Physical Vices, Superstitions, and Selfish Ambitions. These have become possible through excess of emotional, and deficiency of rational states of the mind. When a large part of a population is influenced by emotional rather than by rational modes of thought, unethical conduct has full opportunity, and suffering and destruction are sure to follow. All races and nations are subject to such disorders, if only in some cases during their periods of infancy and of degeneracy.