general, as impenetrability or space-occupancy. special, as the forms resulting from molecular equilibrium. giving statico-dynamical properties of matter (cohesion, elasticity, etc.) when solid. when liquid. when gaseous. when not in equilibrium: (_Molecular Dynamics_) as resulting in a changed distribution of molecules which alters their relative positions homogeneously causing increase of volume (expansion, liquefaction, evaporation). causing decrease of volume (condensation, solidification, contraction). which alters their relative positions heterogeneously (_Chemistry_) producing new relations of molecules (new compounds). producing new relations of forces (new affinities). as resulting in a changed distribution of molecular motion, which, by integration, generates sensible motion. which, by disintegration, generates insensible motion, under the forms of {_Heat._ _Light._ _Electricity._ _Magnetism._} Wecome now to the third great group. We have done with the Sciences which are concerned only with the blank forms of relations under which Being is manifested to us. We have left behind the Sciences which, dealing with Being under its universal mode, and its several non-universal modes regarded as independent, treat the terms of its relations as simple and homogeneous; which they never are in Nature. There remain the Sciences which, taking these modes of Being as they are habitually connected with one another, have for the terms of their relations, those heterogeneous combinations of forces that constitute actual phenomena. The subject-matter of these Concrete-Sciences is the real, as contrasted with the wholly or partially ideal. It is their aim, not to separate and generalize apart the components of all phenomena, but to explain each phenomenon as a product of these components. Their relations are not, like those of the simplest Abstract-Concrete Sciences, relations between one antecedent and one consequent; nor are they, like those of the more involved Abstract-Concrete Sciences, relations between some few antecedents cut off in imagination from all others, and some few consequents similarly cut off; but they are relations each of which has for its terms a complete plexus of antecedents and a complete plexus of consequents. This is manifest in the least involved Concrete Sciences. The astronomer seeks to explain the Solar System. He does not stop short after generalizing the laws of planetary movement, such as planetary movement would be did only a single planet exist; but he solves this abstract-concrete problem, as a step towards solving the concrete problem of the planetary movements as affecting one another. In astronomical language, “the