You asked about the substrate that is the continuum underlying life and death and is our immortality. This would be the ‘spirit that rolls through all things’ Wordsworth feels in his heart as he walks around Tintern Abbey in the Wye valley, the very same spirit you feel as you walk the woods paying attention to life and the Great Spirit of the native Americans, the One that is All known as Wakantanka.
This substrate or Source would be the only phenomena that is truly real. It would be everywhere at all times because the extended space-time world would not be truly real. This is what we learn in Buddhist practice if we have some success. This would be how God is able to watch every sparrow that falls. He would be unable not to watch.
Human beings would not be exceptions to the rule. Lao Tsu is able to know the truth about the origin of creation by ‘looking inside himself’. Inside us, prior to our intellect and discursive mind, and cleverly veiled by our intellect and discursive mind, would be the source of our intellect and discursive mind. This is not subject to life and death.
A brief way of stating all this is to say that Reality is a Unity, but this word often causes misunderstandings. It is not easy to understand the meaning of ‘Unity’ and at limit impossible. To properly know the intended meaning of this word we would have to properly know the true nature of
Reality.
We can know this because we are Reality. What else could we be? ‘Within’ each of us, prior to our sense of individuality, is a spark of God, the pristine awareness, let us say, from which the world emerges. Without this spark we are nothing. Thus Iman Ali, the first Shia Imam, asks us why we think we are puny beings when ‘within us the universe is enfolded’.
The only way to know this substrate is to ask ‘Who am I?’ and keep asking until we find out.
Nagarjuna proves that this Ultimate has no positive attributes or properties and is a Unity in this sense or, as Plotinus puts it, a ‘One with no Second’. This would be why metaphysics does not endorse a positive result.
Thus you simply are this substrate and Ultimate. That is to say, as Schrödinger puts it, ‘I am God’ as are you. The appearance of ‘you’ and ‘me’ would be just that, an appearance. As such it is possible to look beyond. The Ultimate, Brahman, Wakantanka or Source, the goal to which Buddhist aspire, is not, as Jesus puts is, ‘Lo! Here or Lo! There’. It is who we are. It seems obvious that everything is Reality but it’s quite easy to forget.
This would be the reason why anyone is capable of feeling ‘the spirit that rolls through all things’, whether they are on the plains of the mid-West before the white man arrived, on the Tibetan plateau in 500 BC, roaming the hills outside Jerusalem at the time of Jesus or right this minute wherever we happen to be. It is an omnipresence. A full realisation of this is said to be our birthright. Not a gift of God to His selected cronies but our inevitable destination if we persevere.
We can all sense The Great Spirit of the native Americans to some degree as an intuition or feeling, but those who never walk in the quiet woods paying attention, or never stand in wonder and awe under a starlit night sky, as is becoming increasingly difficult to do in this decadent age, may, I suspect, lose their ability to tune in to the Great Spirit, which is to say their inner feelings and intuitions that point to their true nature. .
Thus I fear for the future, or would if I thought the global economy was going to survive much longer. Martin Heidegger expresses the same fear as early as the 1930’s, foretelling that Man will become so entranced by all his fancy new gadgets in this atomic age He would lose his abilities and forget He is an essentially meditative species.