Karma is manifestation of will

Swami Vivekananda says :

All the actions that we see in the world, all the movements in human society, all the works that we have around us, are simply the display of thought, the manifestation of the will of man. Machines or instruments, cities, ships, or men-of-war, all these are simply the manifestation of the will of man; and this will is caused by character, and character is manufactured by Karma. As is Karma, so is the manifestation of the will.

The men of mighty will the world has produced have all been tremendous workers – gigantic souls, with wills powerful enough to overturn worlds, wills they got by persistent work, through ages, and ages. Such a gigantic will as that of a Buddha or a Jesus could not be obtained in one life, for we know who their fathers were. The gigantic will which Buddha and Jesus threw over the world, whence did it come? Whence came this accumulation of power? It must have been there through ages and ages, continually growing bigger and bigger, until it burst on society in a Buddha or a Jesus, even rolling down to the present day. (I, 30 – 31)