What is meaning of heart here?

Question

I was reading following line from This link

'As all waters find their centre in the sea, all touches in the skin, all tastes in the tongue, all smells in the nose, all colours in the eye, all sounds in the ear, all percepts in the mind, all knowledge in the heart, all actions in the hands, all movements in the feet, and all the Vedas in speech

It says all knowledge at heart (it's clear that heart doesn't mean heart the organ), then what is heart here.

Also is there any difference(s) between buddhi,chitta,smriti,mana,pragya. What are these differences (please give answer with definitions for each).

Answer 1

The following is another perspective for this verse:

Does Heart mean the physical heart?

Actually the Heart mentioned by the text does not mean literally the physical blood pumping organ in the body.

Rather it means the spiritual heart.

This is what Sri Ramana Maharishi says in this matter [Reference]:

[The Heart] is the Centre of spiritual experience according to the testimony of Sages. The spiritual Heart-centre is quite different from the blood- propelling, muscular organ known by the same name. The spiritual Heart-centre is not an organ of the body. All that you can say of the Heart is that it is the very Core of your being, that [with] which you are really identical (as the word in Sanskrit literally means), whether you are awake, asleep or dreaming, whether you are engaged in work or immersed in Samadhi. (Ramana Maharshi, MG, 73.)

The Heart … is different from the blood vessel, so called, and is not the Anahata Chakra in the middle of the chest, one of the six centres spoken of in books on Yoga. (Ramana Maharshi, KOL, 150.)

This heart is different from the physical heart; beating is the function of the latter. The former is the seat of spiritual experience. That is all that can be said of it.

So what does the Heart as the center or cause of all knowledge?

So in other words Heart here does not refer to the physical heart, but the Heart of our being. The spiritual heart. It is actually the consciousness which is the core of our being, thus it is called as Heart since it is the cause of all causes.

Now why is it that knowledge finds its seat in the Heart?

This is because it is from consciousness that all knowledge arises. If you do not know that you exist, then you cannot know anything else. Thus this consciousness is the core and the cause of all knowledge. This consciousness is the Heart.

Sri Swami Krishnananda says in the Philosophy of Life, Theory of Perception as that:

The real seer and the senser of things is this consciousness which is at the background of the perceiving subject as its existence and essence. The ultimate knower of the world is an absolute being whose presence is established by the nature of knowledge itself.

What is the difference between Manas, Buddhi, Chitta and Prajna?

Buddhi - Buddhi means the intellect. It is the Mind engaging in analysis and discrimination.

Manas - Manas implies the emotional nature of the Mind. The Mind with its thoughts and emotions is called Manas.

Chitta - Chitta essentially means the subconscious mind. It is literally translated 'mind-stuff'. It is the Mind which penetrates into a very subtle realms.

Prajna - Prajna is pure wisdom. According to Mandukya Upanishad, the causal body (karana sarira) where the Mind-stuffs dissolves and only a mass of consciousness remains, is called Prajna. In this state there is an abundance of bliss called anandamaya. This is called Prajna. [Mandukya Upanishad, 5]

Essentially speaking, manas, buddhi and chitta all refer to the Mind. But they are used to highlight various modes or functions of the Mind. In essence there is only the Mind. This Mind when it engages in intellectual stuff is called Buddhi, when emotional, it is called Manas, and when generally speaking, it is called chitta. [Here is more information about these various faculties - Various modes of Mind] All the best!

Answer 2

You can read Adi Shankaracharya's commentary on the this Brihadaranyaka Upanishad chapter here. This is what he says about "all touches in the skin" part; the other parts of the quote are analogous:

Likewise as the skin is the one goal of all kinds of touch such as soft or hard, rough or smooth, which are identical in nature with air. By the word ‘skin,’ touch in general, which is perceived by the skin, is meant; in it different kinds of touch are merged, like different kinds of water in the ocean, and become nonentities without it, for they were merely its modifications. Similarly that touch in general, denoted by the word ‘skin,’ is merged in the deliberation of the Manas, that is to say, in a general consideration by it, just as different kinds of touch are included in touch in general perceived by the skin; without this consideration by the Manas it becomes a nonentity.

According to Adi Shankaracharya, the word "skin" is being used as an analogy for touch in general, because touch in general is perceived in the skin. So he's saying that it means that all different kinds of touches are dissolved into the general category of touch by the act of contemplation. In the same way, the "all knowledge in the heart" part would mean that all different kinds of knowledge are dissolved into the general category of knowledge by the act of contemplation.

So now the only question is why the word "heart" is being used as a metaphor for the general category of knowledge. Well, in analogy to the touch case, it would have to be because knowledge in general is perceived in the heart. And what does that mean? It's probably a reference to the fact that the heart is the dwelling-place of the soul. This is attested in multiple places, for in this chapter of the Katha Upanishad:

There are the two, drinking their reward in the world of their own works, entered into the cave (of the heart), dwelling on the highest summit (the ether in the heart). Those who know Brahman call them shade and light; likewise, those householders who perform the Trinâkiketa sacrifice.

And this chapter of the Chandogya Upanishad:

There is this city of Brahman (the body), and in it the palace, the small lotus (of the heart), and in it that small ether. Now what exists within that small ether, that is to be sought for, that is to be understood.

(I discuss that Chandogya Upanishad quote in my question here, because some people claim that it's a prophecy of Chaitanya Mahaprabhu.)