This whole debate is a product of the deeply ingrained and grammatically incomprehensible Trinitarian doctrine, which some of its most famous exponents, such as the German theological Karl Rahner in his The Trinity [1970, pp 113-14], teach as “the one God [of the Jewish-Christian Shema, Deu 6.4; Mar 12.29] subsisting [existing] as three distinct persons [hypostasis]…the Father, the Son, the Spirit…hence these ‘three’ are not the same ‘one’”. This doctrine is a product of the ancient Catholic creedal statements composed during the 4th-6th centuries first under the pagan, turned Christian sympathizer, Roman Emperor Constantine.
Apart from the fact that such Trinitarian statements have obvious theological holes, I’d like to argue from scripture [and not from Catholic creeds] why YHWH, the God and Father of our lord Messiah Jesus, is not a “What” [an essence, ousia] but one “Who”!
Similar to His creatures, YHWH is described in the Bible as having a “soul” [Lev 26.11, 30; Zech 11.8; Isa 1.14; Jer 32.41] and a “spirit” [Gen 6.3; Isa 42:1; Neh 9.30]. The word often translated “soul” comes from the Hebrew nephesh, a “feminine noun [that] is used 753 times in the Old Testament and has a broad range of meanings. Most of its uses fall into these categories:
• breath, literally or figuratively (Jer 15:9);
• the inner being with its thoughts and emotions (Jdg 10:16; Pro 14:10; Eze 25:6);
• and by extension, the whole person (Gen 12:5; Lev 4:2; Eze 18:4).”
Now the word translated “spirit” is likewise a “feminine noun [which also signifies breath and wind]. The word is used to refer to the "Spirit of God" or "the LORD"…properly referred to as the Holy Spirit (Psa 51:11; 106:33; Isa 63:10-11).” The point is that these words are expressive of the whole person of God [cp. Deu 26.16; Joshua 10.39].
When scripture describes YHWH in such terms it should communicate to the reader that we are dealing with one single personal being, and not some non-personal “spiritual nature” — certainly not one “what” or one “essence.”
It is important to define God as a “Person.” We must not represent the God of the Bible as one What. The developed doctrine of the Trinity led to non-biblical, philosophical language of nature, being, substance and redefinition of “persons” as found in the creeds.
Scripture tells us that although YHWH is described as a “spiritual being”, He is also said to have this spirit within Him. This concept may be confusing for some since Jesus tells us that “God is spirit” [John 4.24]. So we must keep in mind that the spirit of God [an expression of His character, mind and Person] is the one and the same Person of God.
In other words, while “God is spirit”, God also has a spirit that is said to work and communicate to us [cp. John 14.15f.]. This is parallel to the Johannine saying that “God is love” [1 John 4.8] or “God is light” [1 John 1.5]. Again, these are qualities that are perfectly expressed and manifested in the one personal God.
“But God has revealed [His promise, purpose, plan, gospel etc.] to us through the spirit, for the spirit searches all things, even the deep things of God. For who among men knows the things of a man, except the spirit of the man, which is in him? Even so [in the same manner] the things of God no one has known, except the Spirit of God. But we received, not the spirit of the world, but the spirit that is from God, in order that we might know the things that were freely given to us by God.” 1Cor 2.10-13
The same idea is also present in the NT when the Apostle Paul prays “that the God of peace Himself…keep your whole spirit and soul and body” holy until the coming of the lord Jesus Christ [1Thess 5.23].
“Spirit, soul, and body represent the entirety of [a human person]. It seems unlikely that this is a tripartite division of human nature into body, soul, and spirit, where ‘spirit’ and ‘soul’ would refer to different parts; more likely Paul is simply using several terms for emphasis. For similar ways of expressing the totality of [a human person] see Matt. 10:28; Mark 12:30; 1 Cor. 7:34.”
“YHWH, the God of the breath of all flesh…In His hand is the life of every living thing and breath of all mankind…For I will not contend forever, nor will I always be angry, for the spirit would grow faint before Me, and the breath of life that I made.” Num 27.16; Job 12.10; Isa 57.16
 See Merriam-Webster Dictionary.
 All quotes from nephesh & ruach found in The WordStudy Dictionary.
 Revised English Version by Spirit & Truth Fellowship International.
 ESV Study Bible.