10 these things God has revealed to us through the Spirit. For the Spirit searches everything, even the depths of God. 11 For who knows a person's thoughts except the spirit of that person, which is in him? (1 Cor 2:10-11).
i) The word "spirit" and "spiritual" are conventional theological jargon in English usage. Problem is, in popular English usage, these words have vague or opaque connotations. What does "spirit" mean? What does "spiritual" mean? I assume this convention comes to us via Latin theology or the Vulgate in particular. "Spiritus".
ii) In 1 Cor 2:11, Paul uses an implicit body/soul analogy. The Spirit's relationship to God is analogous to the soul's relationship to the body. Outsiders can't read your mind. Only you have direct access to your own mind. According to the analogy, the God's Spirit is akin to God's soul (if God had a soul).
There's the additional principle that "like knows like" (a point made by Fitzmyer). Only God can truly reveal God.
In this passage, Paul uses "spirit" for both the divine and human referents for linguistic continuity in the comparison. In addition, the "Spirit [pneuma] of God" is a conventional designation, via the LXX.
But conventional designations aside, it's clear that he's comparing the human mind to the divine mind. He's using "spirit" as a synonym for "mind" (or intellect).
iii) If, instead of the "Spirit of God," we used the "Mind of God" to designate the third person of the Trinity, that would instantly dissolve the ambiguity of the linguistic convention. There's no doubt that the "mind of God" must be both personal and divine.
iv) But how can the third person of the Trinity be the mind of God? Surely the Father and the Son aren't mindless individuals.
To some degree, we need to make allowance of the limitations of Paul's analogy. However, even though it sounds paradoxical, a mind can engage in self-reflection. Paul is trading on the human experience of introspection. A mind can be the object of its own consideration. A mind can be both subject and object. Like when we search our memories. And Paul is saying God is like that.
v) The thought in v11 underscores the thought in v10. Because only God can know his own mind, so only God can reveal what's on his mind.
vi) On this analysis, "spiritual" means, at least in part, "mental" (or psychological), in contrast to physical or material. In biblical usage, I'd also say it has connotations of sanctity or holiness. "Spiritual" stands in contrast to sinful.
Indeed, the two go together inasmuch as the mind is the primary theater for sin. Sin begins with sinful thoughts and impulses. In some cases the sinner acts on his thoughts and impulses. In that event, the action takes place in the world of space.