Although the spirit is not as matter, it cannot be measured like energy can be measured though unseen, this poor example can assist one's understanding.
Water exists in three states: as a solid (ice), a liquid (liquid) and a gas (vapor).
Some may have argued out of ignorance many years ago, knowing only water as something they drink, that there is no possible way that water can be a solid (ice) nor a gas (invisible vapor).
Prior to any man visiting the snow (for example, peoples who have lived their entire lives in the African central region, or perhaps in the vast desserts of the Arabian peninsula who have never traveled to a mountain top and seen snow), the idea of ice prior to the modern age would be an impossibility.
Maybe when first visiting the snow, or seeing ice, they would wonder how water can become a solid or return to being a liquid.
The same can be said regarding water as a gas (vapor).
Since a vapor cannot be seen, some people long ago may have been apt to say once water is gone (evaporates) it doesn't exist anymore...but today we know different.
Mankind has come to realize, understand and declare that water (as with energy) doesn't simply 'die' or go away, but simply changes form...or its state of being.
The same can be said when the carnal mind considers the mystery of God in Christ, and God in man; the revealing of God as more than what humans would typically consider and accept.
Why is this?
These are the things God has revealed to us by His Spirit.
The Spirit searches all things, even the deep things of God. For who knows a person’s thoughts except their own spirit within them? In the same way no one knows the thoughts of God except the Spirit of God. What we have received is not the spirit of the world, but the Spirit who is from God, so that we may understand what God has freely given us. This is what we speak, not in words taught us by human wisdom but in words taught by the Spirit, explaining spiritual realities with Spirit-taught words. The person without the Spirit does not accept the things that come from the Spirit of God but considers them foolishness, and cannot understand them because they are discerned only through the Spirit. The person with the Spirit makes judgments about all things, but such a person is not subject to merely human judgments, for,
“Who has known the mind of the Lord
so as to instruct Him?”
But we have the mind of Christ.
- 1 Corinthians 2: 10-16
So just as the person who has not been given ice in their water glass, or hasn't learned that the ice first becomes water and then turns to a vapor (or vice versa)...only to repeat the process elsewhere, so the person without God's gift of faith (the Spirit) cannot understand and fully comprehend how God can become a man without becoming divided into two or three (when considering His Holy Spirit), for all these three states of God have always been One, as water is always one while existing in three states at all times.