perceive the possibility of a mixture of colours; the affection, the
intellect, the devotion may be tinged by selfishness, and in that case
their distinctive colours are mingled with the brown of selfishness, and so
we have an impure and muddy appearance. Although its particles are always
in intensely rapid motion among themselves, this body has at the same time
a kind of loose organization.

The size and shape of the mental body are determined by those of the causal
vehicle. There are in it certain striations which divide it more or less
irregularly into segments, each of these corresponding to a certain
department of the physical brain, so that every type of thought should
function through its duly assigned portion. The mental body is as yet so
imperfectly developed in ordinary men that there are many in whom a great
number of special departments are not yet in activity, and any attempt at
thought belonging to those departments has to travel round through some
inappropriate channel which happens to be fully open. The result is that
thought on those subjects is for those people clumsy and uncomprehending.
This is why some people have a head for mathematics and others are unable
to add correctly--why some people instinctively understand, appreciate and
enjoy music, while others do not know one tune from another.

All the matter of the mental body should be circulating freely, but
sometimes a man allows his thought upon a certain subject to set and
solidify, and then the circulation is impeded, and there is a congestion
which presently hardens into a kind of wart on the mental body. Such a wart
appears to us down here as a prejudice; and until it is absorbed and free
circulation restored, it is impossible for the man to think truly or to see
clearly with regard to that particular department of his mind, as the
congestion checks the free passage of undulations both outward and inward.