Dementia is a disease affecting the brain. So then you need a fully functioning brain in order to be able to get the Jhanas? Is there an actual definition of what the mind is in the suttas? Sorry, I'm fairly new to all this and trying to understand it is giving me brain damage
You need a functioning brain in order to do
anything in this human life - I think this is obvious ))
As for the definition - this is somewhat complex question, because several other terms need to be explained here as well (connected with the mind) - such as mano, vinnyana, citta, nama, etc. But what can be said for sure is that mind is one thing, and body is another.
From MN 77 sutta:
“Again, Udayin, I have proclaimed to my disciples the way to understand thus: ‘This body of mine, made of material form, consisting of the four great elements, procreated by a mother and father, and built up out of boiled rice and porridge, is subject to impermanence, to being worn and rubbed away, to dissolution and disintegration, and this consciousness of mine is supported by it and bound up with it.’ Suppose there were a beautiful beryl gem of purest water, eight-faceted, well cut, clear and limpid, possessed of all good qualities, and through it a blue, yellow, red, white, or brown thread would be strung. Then a man with good sight, taking it in his hand, might review it thus: ‘This is a beautiful beryl gem of purest water, eight-faceted, well cut, clear and limpid, possessed of all good qualities, and through it is strung a blue, yellow, red, white, or brown thread.’ So too, I have proclaimed to my disciples the way to understand thus: ‘This body of mine…is subject to impermanence, to being worn and rubbed away, to dissolution and disintegration, and this consciousness of mine is supported by it and bound up with it.’ And thereby many disciples of mine abide having reached the consummation and perfection of direct knowledge".
And this is SN 55.21:
When a person’s mind has been fortified over a long time by faith, virtue, learning, generosity, and wisdom, right here crows,vultures,hawks,dogs,jackals,or various creatures eat his body, consisting of form, composed of the four great elements, originating from mother and father, built up out of rice and gruel, subject to impermanence, to being worn and rubbed away away, to breaking apart and dispersal. But his mind, which has been fortified over a long time by faith,virtue,learning,generosity, and wisdom—that goes upwards, goes to distinction. “Suppose, Mahanama, a man submerges a pot of ghee or a pot of oil in a deep pool of water and breaks it. All of its shards and fragments would sink downwards, but the ghee or oil there would rise upwards. So too, Mahanama, when a person’s mind has been fortified over a long time by faith, virtue, learning, generosity,and wisdom,right here crows… or various creatures eat his body.… But his mind, which has been fortified over a long time by faith, virtue, learning, generosity, and wisdom—that goes upwards, goes to distinction".