_Manas_, or the Thinker, is the reïncarnating being, the immortal who carries the results and values of all the different lives lived on earth or elsewhere. Its nature becomes dual as soon as it is attached to a body. For the human brain is a superior organism and _Manas_ uses it to reason from premises to conclusions. This also differentiates man from animal, for the animal acts from automatic and so-called instinctual impulses, whereas the man can use reason. This is the lower aspect of the Thinker or _Manas_, and not, as some have supposed, the highest and best gift belonging to man. Its other, and in theosophy higher, aspect is the intuitional, which knows, and does not depend on reason. The lower, and purely intellectual, is nearest to the principle of Desire, and is thus distinguished from its other side which has affinity for the spiritual principles above. If the Thinker, then, becomes wholly intellectual, the entire nature begins to tend downward; for intellect alone is cold, heartless, selfish, because it is not lighted up by the two other principles of _Buddhi_ and _Atma_. In _Manas_ the thoughts of all lives are stored. That is to say: in any one life, the sum total of thoughts underlying all the acts of the life-time will be of one character in general, but may be placed in one or more classes. That is, the business man of to-day is a single type; his entire life thoughts represent but one single thread of thought. The artist is another. The man who has engaged in business, but also thought much upon fame and power which he never attained, is still another. The great mass of self-sacrificing, courageous, and strong poor people who have but little time to think, constitute another distinct class. In all these the total quantity of life thoughts makes up the stream or thread of a life’s meditation—“that upon which the heart was set”—and is stored in _Manas_, to be brought out again at any time in whatever life the brain and bodily environments are similar to those used in engendering that class of thoughts.