*Glimpses of Self-Realization* - ‘WHO AM I?’ (extracts) - Collected Works - Of all thoughts that arise in the mind, the thought 'I' is the first one. It is only after the rise of this [thought] that other thoughts arise. It is only after the first personal pronoun arises that the second and third personal pronouns appear. Without the first person, the second and third persons cannot exist - Ramana Maharshi

Every living being longs to be perpetually happy, without any misery. Since in everyone the highest love is alone felt for oneself, and since happiness alone is the cause of love, in order to attain that happiness, which is one's real nature and which is experienced daily in the mindless state of deep sleep, it is necessary to know oneself. To achieve that, inquiry in the form 'Who am I?' is the foremost means.

'Who am I?' The physical body, composed of the seven dhatus, is not 'I'. ...
Even the mind that thinks is not 'I'. In the state of deep sleep vishaya vasanas remain. Devoid of sensory knowledge and activity, even this [state] is not 'I'. After negating all of the above as 'not I, not I', the knowledge that alone remains is itself 'I'. The nature of knowledge is sat-chit-ananda [being-consciousness-bliss].

If the mind, which is the cause of all knowledge and all actions, subsides, the perception of the world will cease. ...

That which is called 'mind', which projects all thoughts, is an awesome power existing within the Self, one's real nature. If we discard all thoughts and look [to see what remains when there are no thoughts, it will be found that] there is no such entity as mind remaining separate [from those thoughts]. Therefore, thought itself is the nature of the mind. There is no such thing as 'the world' independent of thoughts. ...
Consequently, when the world appears, the Self is not seen, and when the Self appears or shines, the world will not appear.

That which arises in the physical body as 'I' is the mind. If one inquires, 'In what place in the body does this ''I'' first arise?' it will be known to be in the hridayam. That is the birthplace of the mind. Even if one incessantly thinks 'I, I', it will lead to that place. Of all thoughts that arise in the mind, the thought 'I' is the first one. It is only after the rise of this [thought] that other thoughts arise. It is only after the first personal pronoun arises that the second and third personal pronouns appear. Without the first person, the second and third persons cannot exist.

Collected Works- Ramana Maharshi