Substance of the spirit

I was reading on page 68 of The Spritiual Man, CFP white cover, Volume 2, "These three are merely functions of the spirit...the main functions of the spirit...None of them is the spirit, for the spirit itself is substantial, personal, invisible. It is beyond our present comprehension to apprehend the substance of the spirit. What we today know of its substance comes via its various manifestations in us."

Intuitively in the spirit, when reading, something pops up in your mind, though related to the subject, so that is how you know it is of the Holy Spirit in agreement with the Word and not an abrupt interjection.

What popped up was "God the Father, God the Son and God the Spirit are of one substance." What Nee said about our spirit regarding the usage of substance of the spirit is similar to what we mean by substance of God's 3 Persons in that we know the substance exists, except that it is beyond our comprehension. Even so, we can understand some things, such as God's 3 Persons.

To reiterate, there is a point where God says it is beyond our comprehension, like a dog staring up at us as we explain a math equation can never know some things.