There are two types of Organisms viz., the ones with consciousness and those without. The latter includes the plants which are produced, grow and finally die, whereas the conscious organisms include the humans and other animals. The organisms with consciousness are called beings because of their unique property of possessing Mind that causes the feeling of ‘I am’ or ‘Being me’; this differentiates the beings from those without mind.
When the Organisms like plants die they are dissolved back into their material constituents and have no stream-of-being, whereas the ones with consciousness or mind could have their stream-of-being in continuation to a new body after their death in their previous life. This apparent difference is due to the presence of mind in one and not in the other. Therefore, a conscious being is considered a collection of both body and mind.
Someone might ask what is the evidence in favor of the fact that the mind pre-exist the individual and continues to exist after death. In Buddhism we think that every things has a cause, as it is logical to assume. A physical phenomenon has a physical cause, a not physical phenomenon must have a not physical cause. The mind, that is not made of a physical substance, must be caused by a non-physical substance; therefore by a previous mind, as the logic leads to the conclusion. Certainly, in this perspective, mind and brain are not the same. And how can we say that? First of all it must be said that this fact is quite obvious to experienced practitioners of meditation. Then there are many testimonies that tell of seeing dead yogins to maintain the posture of meditation for days; this can be explained only by the fact that the mind was still working despite the body and brain were dead. What about the stories of people under anesthesia have reported seeing from above the unfolding of the surgery in detail? Obviously in these cases the sleeping brain could not work but the mind worked.
The main function of the mind is to know: a being has two modes of knowing, one is the direct mode of perception and other the indirect mode of reasons.
The object of the direct perception could be categorized into form, sound, smell, taste and touch. According to Buddhist presentation, form and so on is perceived by three primary agents the object, governing condition and immediately preceding condition.
For instance, the form is perceived by the collective effect of the form object being perceived, the governing condition eye sense and the immediately preceding condition eye consciousness. Similarly, other objects like sound, smell etc could be perceived with their respective object, governing condition and immediately preceding condition. Therefore, the five consciousnesses, viz., eye consciousness, ear consciousness and so on perceive their respective object viz., form, sound and so on with the help of their respective senses viz., eye sense, ear sense and so on. As per modern understanding the human attributes like perception, behavior and feelings could be explained on the basis of the neural networks of Brain. If that is the case, every human attribute could have been explained through material observations and the corresponding tools. Of course Brain is an integral agent, similar to the governing condition as alluded, for human emotions and perception nevertheless it facilitates the mind, just as a Mobile phone does to carry the voice from the other end.