The question of the reality of the external world did not present itself to the early Buddhists.  Had it been posed we may surmise that the Buddha would have replied, as in similar cases, that the question was not properly put.  He would not, we may imagine, have admitted that the human mind has the creative power which idealism postulates, for such power seems to imply the existence of something like a self or atman.  But still though the Pitakas emphasize the empirical duality of sense-organs and sense-objects, they also supply a basis for the doctrines of Nagarjuna and Asanga, which like much late Buddhist metaphysics insist on using logic in regions where the master would not use it.  When it is said that the genesis of the world and its passing away are within this mortal frame, the meaning probably is that the world as we experience it with its pains and pleasures depends on the senses and that with the modification or cessation of the senses it is changed or comes to an end.  In other words (for this doctrine like most of the Buddha’s doctrines is at bottom ethical rather than metaphysical) the saint can make or unmake his own world and triumph over pain.  But the theory of sensation may be treated not ethically but metaphysically.  Sensation implies a duality and on the one side the Buddha’s teaching argues that there is no permanent sentient self but merely different kinds of consciousness arising in response to different stimuli.  It is admitted too that visible objects are changing and transitory like sight itself and thus there is no reason to regard the external world, which is one half of the duality, as more permanent, self-existent and continuous than the other half.  When we apply to it the destructive analysis which the Buddha applied only to mental states, we easily arrive at the nihilism or idealism of the later Buddhists.  Of this I will treat later.  For the present we have only to note that early Buddhism holds that sensation depends on contact, that is on a duality.  It does not investigate the external part of this duality and it is clear that such investigation leads to the very speculations which the Buddha declared to be unprofitable, such as arguments about the eternity and infinity of the universe.

The doctrine of Anatta is counterbalanced by the doctrine of causation.  Without this latter the Buddha might seem to teach that life is a chaos of shadows.  But on the contrary he teaches the universality of law, in this life and in all lives.  For Hindus of most schools of thought, metempsychosis means the doctrine that the immortal soul passes from one bodily tenement to another, and is reborn again and again:  karma is the law which determines the occurrence and the character of these births.  In Buddhism, though the Pitakas speak continually of rebirth, metempsychosis is an incorrect expression since there is no soul to transmigrate and there is strictly speaking nothing but karma.  This word, signifying literally action