- 2) Powers of the Mind - The Plane Of Creation

(Wm. Q. Judge-Ocean of Theosophy, P. 52 )
The fifth principle is Manas, in the classification adopted by Mr. Sinnett, and is usually translated Mind. Other names have been given to it, but it is the knower, the perceiver, the thinker.

(Wm. Q. Judge- Ocean of Theosophy, P. 54)
It is Manas which sees the objects presented to it by the bodily organs and the actual organs within. When the open eye receives a picture on the retina, the whole scene is turned into vibrations in the optic nerves which disappear into the brain, where Manas is enabled to perceive them as idea. And so with every other organ or sense. If the connection between Manas and the brain be broken the astral body from the physical and thereby keep up communication with fellowmen, intelligence will not be manifested unless Manas has by training found out how to project the astral body from the physical and thereby keep up communication with fellowmen.

(Wm. Q. Judge- Ocean of Theosophy, P. 56)
It is this lower Manas which retains all the impressions of a life-time and sometimes strangely exhibits them in trances or dreams, delirium, induced states, here and there in normal conditions, and very often at the time of physical death. But it is so occupied with the brain, with memory and with sensation, that it usually presents but few recollections out of the mass of events that years have brought before it. It interferes with the action of Higher Manas because just at the present point of evolution, Desire and all corresponding powers, faculties, and senses are the most highly developed, thus obscuring, as it were, the white light of the spiritual side of Manas. It is tinted by each object presented to it, whether it be a thought-object or a material one. That is to say, Lower Manas operating through the brain is at once altered into the shape and other characteristics of any object, mental or otherwise. This causes it to have four peculiarities.

• First, to naturally fly off from any point, object, or subject;
• Second, to fly to some pleasant idea;
• Third, to fly to an unpleasant idea;
• Fourth, to remain passive and considering naught
  

(HPB, Secret Doctrine, Vol. I, p. 292)
(2.) JNANASAKTI. . . . The power of intellect, of real Wisdom or Knowledge. It has two aspects:
The following are some of its manifestations when placed under the influence or control of material conditions. (a) The power of the mind in interpreting our sensations. (b) Its power in recalling past ideas (memory) and raising future expectation. (c) Its power as exhibited in what are called by modern psychologists "the laws of association," which enables it to form persisting connections between various groups of sensations and possibilities of sensations, and thus generate the notion or idea of an external object. (d) Its power in connecting our ideas together by the mysterious link of memory, and thus generating the notion of self or individuality; some of its manifestations when liberated from the bonds of matter are -- (a) Clairvoyance, (b) Psychometry.

(HPB-Transactions of the Blavatsky Lodge, p. 27)
Q. What is meant by the term instinctual mind?
A. The instinctual mind finds expression through the cerebellum, and is also that of the animals. With man during sleep the functions of the cerebrum cease, and the cerebellum carries him on to the Astral plane, a still more unreal state than even the waking plane of illusion; for so we call this state which the majority of you think so real. And the Astral plane is still more deceptive, because it reflects indiscriminately the good and the bad, and is so chaotic.
Q. The fundamental conditions of the mind in the waking state are space and time: do these exist for the mind (Manas) during the sleep of the physical body?
A. Not as we know them. Moreover, the answer depends on which Manas you mean -- the higher or the lower. It is only the latter which is susceptible of hallucinations about space and time; for instance, a man in the dreaming state may live in a few seconds the events of a life-time.

(Wm. Q. Judge-Patanjali's Yoga Aphorisms, P. 2)
…. the want of concentration of thought is due to the fact that the mind -- here called "the thinking principle" -- is subject to constant modifications by reason of its being diffused over a multiplicity of subjects. So "concentration" is equivalent to the correction of a tendency top, diffuseness, and to the obtaining of what the Hindus call "one-pointedness," or the power to apply the mind, at any moment, to the consideration of a single point of thought, to the exclusion of all else.

Upon this Aphorism the method of the system hinges. The reason for the absence of concentration at any time is, that the mind is modified by every subject and object that comes before it; it is, as it were, transformed into that subject or object. The mind, therefore, is not the supreme or highest power; it is only a function, an instrument with which the soul works, feels sublunary things, and experiences. The brain, however, must not be confounded with the mind, for the brain is in its turn but an instrument for the mind. It therefore follows that the mind has a plane of its own, distinct from the soul and the brain, and what is to be learned is, to use the will, which is also a distinct power from the mind and brain, in such a way that instead of permitting the mind to turn from one subject or object to another just as they may move it, we shall apply it as a servant at any time and for as long a period as we wish, to the consideration of whatever we have decided upon.

(Wm. Q. Judge-Bhagavad Gita, P. 28)
"The senses and organs are esteemed great, but the thinking self is greater than they. The discriminating principle (3) is greater than the thinking self, and that which is greater than the discriminating principle is He. (4) Thus knowing what is greater than the discriminating principle
and strengthening the lower by the Higher Self, do thou of mighty arms slay this foe which is formed from desire and is difficult to seize."

Additional References-
(HPB, Transactions - pp. 65, 68, 22)
(HPB, Key To Theosophy, pp. 90, 183)