That part which does this function in the mental plane is called physical mind. Mind is capable of dwelling on physical objects or non-physical phenomena without resorting to the aid of the physical senses and the channel of sensation that accumulate observed facts. This is the beginning of the birth of knowledge. Birth of knowledge in the mind requires the mind raising itself above the need of sensory experience, resort to the physical senses and in the mind itself, rising above the plane of the physical mind to the centres of thinking mind and ideative mind. Senses dwell on the objects directly, physically.
Mind dwells on the idea about the object.
This capacity of the mind to relate to or dwell on an idea of an object is thinking. Out of this mental endeavour thought is born. Further, when the thinking mind tries to relate two or more such thoughts, the processes of deduction, inference, etc. are born. These are the areas proper to the functioning of thought. When a great many thoughts are co-related by an effort of mind, original thought can arise.