Whatever and whenever there's a 'thinking', or a 'thought', or an 'idea' arises in the mind, thinking and believing and identifying as "I am this or that" and "I am not this or that", it's merely part of the selfless function of the selfless thinking faculty being part of the selfless function of the selfless physical body.
That's why no matter what the thinking faculty thinks and believes and identifies as 'I', or "This is I" and "This is not I", it's incorrect.
That's why in the traditional lineage of zen meditation, the teacher will 'spank' the students regardless of what the student answers or doesn't answer, thinks or doesn't think, believes or doesn't believe, identifies or doesn't identify with something or anything, upon being asked, "Who 'am' I?".
If the self-inquiry or investigation towards "Who 'am' I?" is being replaced with "What 'is' I?", or even more precise, "What is the 'I' that the mind thinks and believes and identifies as 'I' and 'not I', or doesn't think and believe and identify as 'I' and 'not I'?", the mind would be having a clearer approach towards the self-inquiry towards selflessness or 'I'lessness.
There is no 'I' existing to be answering or not answering, to be thinking or not thinking, to be believing or not believing, to be identifying or not identifying with something or anything, including nothing. Such as there's no "I am selfless" if it's something selfless.
More importantly, selflessness without a permanent independent existence of 'I' in the body and mind or in any organism and objects, doesn't mean that the selfless impermanent life existence of a selfless impermanent physical body with the selfless impermanent function of the selfless thinking faculty doesn't exist. It doesn't mean that all these that the selfless thinking faculty is perceiving now, doesn't exist. Neither past nor future, as well as 'all these are not real', also doesn't mean that all these that is happening now in the present moment doesn't exist. But all and everything are existing, changing and ceased existing in this present moment, selflessly and impermanently.
The one that answers or doesn't answer, thinks and doesn't think, believes and doesn't believe, identifies and doesn't identify with something or anything, it's merely the selfless function of a selfless thinking faculty being part of the selfless impermanent existence and function of the selfless impermanent physical body.
Under the presence of the idea of 'I' under the influence of the veil of ignorance, egoism, impurities and restlessness, being conditioned by worldly passionate egoistic thinking, belief, values and practice to be reasoning and understanding everything, the mind couldn't grasp or comprehend towards selflessness.
Many thousand years ago, when 'scientific research' wasn't a common thing in the world, even though science is 'the truth of what things are', that exists forever, regardless of whether human beings know or don't know about what things are, while 'technology' hasn't been well developed yet, where self-inquiry and self-realization towards the truth of selflessness and impermanence was being seen as something 'mystical' and yet 'insane' and 'impossible' for most minds that are functioning under the idea of 'I' under the veil of ignorance, egoism, impurities and restlessness.
All minds that had attained self-realization via self-inquiry and meditation under a calmed and purified modification of the mind towards the truth of selflessness and impermanence in all kinds of names and forms, especially in the complex function of the selfless impermanent physical body that comes with the complex function of the selfless perceptive cognitive intellectual emotional thinking and acting faculty, are all great scientists of the world, even without the help of advanced technology to be performing detailed research onto the formation and function of the mortal selfless impermanent physical body, where they know what many minds don't know, where their way of thinking, reasoning, understanding, desire, behavior, action and reaction are being different from most minds that are still functioning under the idea of 'I', ignorance, egoism, impurities and restlessness, where they are resting in unconditional peace while most minds that are under the influence of ignorance are struggling and drowning in different kinds of suffering, or some minds are even 'enjoying' in generating many kinds of suffering into the world out of ignorance.
However, even though there are many advanced technologies in this era, to be looking into the complex formation and function of the physical body and the thinking faculty, the many highly intelligent and knowledgeable minds that are interested in science or scientific research might still be encountering difficulty towards knowing or comprehending selflessness, as the minds are deeply being ingrained with and conditioned by the worldly passionate egoistic thinking, belief, values and practice that based on the idea of 'I'.
It's not that difficult for the minds to experience, see, know and understand towards the truth of impermanence in all and everything, however, it's a great challenge and even impossible for the mind to experience, see, know and understand the truth of selflessness. That's why the importance of the observation of silence, dispassion and renunciation in seclusion and solitude for activating the mind purification process to free the mind from being conditioned or influenced by worldly passionate egoistic thinking, belief, values and practice based on the idea of 'I', to inquire, investigate, reason and understand everything, as it is.
The idea of 'I', ignorance, egoism, impurities and restlessness, is the root cause of all kinds of humanity problems and behavior problems in the world, that give rise to many kinds of unnecessary painful sorrow and suffering deriving from the existence of corruption, incorrect reasoning and understanding, selfishness, possessiveness, separateness, greed, fear, discrimination, hatred, oppression, conflict, fighting, bullying and violence in the world of many diversities that doesn't belong to anyone or anything.
Just as Swami Sivananda mentioned in his teachings while being a medical doctor himself, "One can cut open the body, and still couldn't find, see or know the mind."
Buddhism, yoga, self-inquiry and meditation, as well as selflessness and impermanence, timelessness and non-separateness, are science.
It's not a belief. It's not a religion. It's not a culture. It's not a ritual. It's not something mystical or untouchable.
It's definitely not just a physical and mental health and beauty and fitness exercise, although it can be, if without dispassion and the renunciation from worldly passionate egoistic thinking, belief, values and practice, and without working on the annihilation of the idea of 'I', ignorance, egoism, impurities and restlessness.
The teachings and practice exists as the selfless guidance and tools for the minds to help and guide itself towards the attainment of self-realization towards the truth of selflessness and impermanence, and thus, be free from the unnecessary suffering deriving from being ignorant towards "Who am I?" or "What is I?", as well as be free from generating hurtful damaging behavior, action and reaction, either wittingly or unwittingly, directly or indirectly, that hurt itself and others and the surrounding environment out of the ignorant selfish disturbed dissatisfied fearful desireful suffering restless states of mind, under the influence of the idea of 'I', ignorance, egoism, impurities and restlessness, during its momentary selfless existence and function in this world of selfless impermanent names and forms.
Inquire towards the truth of everything, including all the teachings of yoga and buddhism that the mind comes in contact with, including all that is here.