192 The Evolution of Mind. 



muscles are in physical work. As a man's power to execute 

 the decrees of his will on brute nature varies with his mus- 

 cular power, so does his power to concentrate his attention, 

 and think, vary in proportion to the size of his frontal lobes. 

 We found elsewhere how the mind obeyed the law of evo- 

 lution by increasing its correspondence with objective facts 

 in time, in space, in heterogenity, in speciality and in gen- 

 erality. Here we discover how it intensifies its activity and 

 reaches toward more and more rapid strides in all these 

 directions by the growth of the power of attention. 



At the very base of its career this power must have been 

 present. As Professor Cope has said, "Physical and men- 

 tal development depend on the will."* To know, requires 

 prolonged experience.! In the rushing stream of Time, 

 what we call Now is but an imaginary line ending the past 

 and verging on the future. To know, includes the past. 

 The absolute present without it is nothing. To embrace 

 the past in knowledge is to remember, but it is also to use 

 attention. Given attention and retained experiences, and 

 we have awareness or consciousness. It may be the lowest 

 type of consciousness, known to us as simple feeling. Will, 

 memory and feeling are thus seen to constitute the indivisi- 

 ble psychic trinity. Matter has a similar trinity in its 

 length, breadth and depth. The evolution of all material 

 forms came by adding atom to atom in three dimensions. 

 The evolution of mentality came by somehow making it 

 possible to expand its three dimensions of feeling, memory 

 or intellect, and will.t How the first of the three grew 

 into its heterogeneity of color and sound, taste and smell, 

 heat and cold, is an unsolvable problem. We know that 

 the difference between the objective causes of yellow and 

 red is speed of vibration. § We do not and probably never 

 will know how the sensation red changes into the sensation 

 green. The same is true of all other sensations. ]STo theory 

 can be framed that will enable us to assimilate them. We 

 may yet by successive analyses discover the psychic steps 

 through which we reached up from the lower to the higher, 

 but farther than this we cannot hope to travel. 



That a distinct unity of composition exists between all 

 our mental states is the positive implication of evolution. 



* American Naturalist, Vol. 21, p. 1128. 

 t Ribot's Diseases of Memory, p. 34. 

 % Bain's Mind and Body, pp. 43, 44. 

 § Lomell's Nature of Light, p. 226. 



