(or matter and energy) are inseparably connected. God is not an external being, acting from without, but a divine power or moving spirit, the cosmos itself; the phenomena of surrounding nature, organic as well as inorganic, are merely different products of one and the same original force, different combinations of one and the same original matter. All the individual objects in the world, all the individual forms of existence, are merely transitory forms of the substance, accidents or modes. These modes are corporeal things, material bodies, when we consider them under the attribute of extension (as filling space); forces or ideas, when we regard them under the attribute of thought (or 'energy'). Matter (the stuff filling space) and energy (the moving force) are two attributes of one substance.
This view Haeckel calls monism, and tries to distinguish from materialism as follows: (1) Our pure monism is neither identical with theoretical materialism, which denies mind and resolves the world into a sum of dead atoms, nor with theoretical spiritualism (recently termed Energetik by Ostwald), which denies matter and regards the world as a spatially arranged group of energies or immaterial natural forces. (2) Matter can never exist and act without mind, nor mind without matter. 'We adhere to the pure and unambiguous monism of Spinoza,' says Haeckel; 'matter, as the infinitely extended substance, and mind (or energy) as the sentient (empfindend) or thinking substance, are the two fundamental attributes or ground properties of the all-embracing divine world-being, the universal substance.
If we interpret Haeckel's system in the light of the preceding statements, we certainly reach a kind of monism. Mind and matter are both aspects of an underlying substance. There is no difficulty in understanding what Haeckel means by the material aspect of the substance: it is the space-filling, extended stuff. It is not so easy to see, however, what the other phase of substance, the mental aspect, is. This attribute the philosopher calls mind or Geist, thought, the sentient side, energy, the moving force. In the chapter on substance we are left under the impression that these attributes are not independent entities, but attributes of something behind them, of a thing in itself called the substance. This impression is strengthened by Haeckel's concluding reflections at the end of his book:
- P. 23.
- 'Monismus,' p. 13.
- 'Weltraethsel,' pp. 249f.
- Weltraethsel,' p. 23. 'Monismus,' p. 27: "For our monism an 'immaterial living spirit' is as unthinkable as a 'dead spiritless matter'; in every atom both are inseparably combined. The other systems conceive force and matter as two essentially different substances."