Broadly, Wittgenstein's Philosophical Investigations are concerned with the nature of consciousness as consciousness. As such, it is akin to both Edmund Husserl's Logical Investigations and Transcendental Logic as well as to Martin Heidegger's " What is Called Thinking.
It also takes direct aim at the fundamental argument put forth by Gottlob Frege's Foundations of Arithmetic" in which Frege strenuously argues against mentalist and psychological theories as the grounding of the concept "number".
In a very specific sense, Wittgenstein's intention is to provide a groundwork for speculation, putting these arguments forth in the passages 339 through 340 as follows:
339. Thinking is not an incorporeal process which lends life and sense to speaking, and which it would be possible to detach from speaking, rather as the Devil took the shadow of Schlemiel from the ground. --- But how "not an incorporeal process"? Am I acquainted with incorporeal processes, then, only thinking is not one of them? No; I called the expression "an incorporeal process" to my aid in my embarrassment when I was trying to explain the meaning of the word "thinking" in a primitive way.
One might say "Thinking is an incorporeal process," however, if one were using this to distinguish the grammar of the word "think" from that of, say, the word "eat". Only that makes the difference between meanings look too slight (It is like saying: numerals are actual, and numbers non-actual, objects.) An unsuitable type of expression is a sure means of remaining in a state of confusion. It as it were bars the way out.
340. One cannot guess how a word functions. One has to look at its use and learn from that.
But the difficulty is to remove the prejudice which stands in the way of doing this. It is not a stupid prejudice.
341. Speech with and without thought is to be compared with the playing of a piece of music with and without thought.
trans. G.E.M Anscombe, Basil Balckwell © 1974
In this metaphorical construction, Wittgenstein presents thinking as a type of gaze. This gaze may or may not be captured in language, but can perceive the function of words, acquiring the meaning. In Husserl, cognition starts with the foundational phenomenon of encountering intentionality of ideas. Heidegger describes thinking as process of consciousness going beyond the thought horizon to authentically encounter Being. Whilst Nietzsche, roots authenticity of Being as an act of Will that unbinds it from the rationality of Apollo, to the free experience of Dionysian dance-music.
What is curious in Wittgenstein's effort to parse this topic is the embarrassment of what might be meant by incorporeal or corporeal. Possibly what he has in mind is Stanisław Leśniewski's calculate of names, a mereology. Where, as with Augustine of Hippo, it is the functioning of behavioral-social framework that binds lexical units to corporality.
The motivation for "corporality" is existential. It may not be Descartes vocabulary, but thinking, in some sense, is existentially real: not fiction. Anselm of Canterbury in his De Grammatico places the existential emphasis on attributes (qualities) not quantities (classes), it is "whiteness" (or virtue) that matters: ontologically, it is the notion of "greater than" that establishes the existential domain as a transfinite condition against the corporal nature. (For elucidation of Anselm's positions in De Gramatico and in his famous "Ontological Argument" using the modern logic of Leśniewski, see D.P. Henry, The Logic of Saint Anslem, Oxford University Press ©1967, and The DeGrammatico of St. Anslem: The Theory of Paronymy, Unversity of Notra Dame Press ©1967). Descartes reserved that, binding existence to egotistical instances.
The difficulty in all this is the misappropriation of the very notions of "existence" and "being". Most do not effectively distinguish. Hence for them to be (satisfying the condition being) means to exist. This is the slippery slope of Heraclitus: things come into or pass out of existence; all is flux and only flux: time as an alinear substrate. However, number (a quality) neither comes into nor passes out of existence, the manifestations given number transitive presence: being.
Existence is the given transcendental condition, it is not many, but one: a singularity that authenticates (or not) the presence and representation.
That thinking is an embarrassment of a fugitive primitive process associated with the corporeal, as Wittgenstein holds, seems strange. A better, more natural to the language about thinking, is that the process of thinking is a reflection of engagement with being, and possibly sometimes with existence. Reflection is a recursive operation that disallows solipsistic constraint and is the iconographic moment that is pregnant semiotic potential, expressed as thought. When the thought-object belong to the domain of being an act that references those objects is possible: words take on index values, and such ontological thought objects, maybe either authentic or fictional. Ontological authenticity is a validation measurement of object-being against the existential.
From an Orthodox Christian perspective, a reflective semiotic approach is core to the theology of icons, whose authenticity is a matter of profound Christology. Gaze and intentionality are reflected into a cosmological instance, and the potential of material entities to be iconographic is created: the material world is understood as a life-bearing reflection of energies. The Latin west's failure to take seriously the synthetic nature of images as boundary markers has resulted in ontological mischeif: the holy mysteries approached as acts of semiotic authentication renders impotent controversies about transubstantiation and symbolism. As such, it is not a historical oddity but the most serious of situtions that lead the Latin west went into schism over azymes producing first the curious innovation of the Laterin IV council and, later, sentimental, if not quiet idosynractric, nominalist analysis of their rites and ritual observances.
Thinking need be neither an embarrassment nor primative process but a volitional action perfomed in an number of different styles, one of serveral cognitive processes. For the purposes of taxonomic disambiguation, what thinking is not is as important than what it is: thinking is not groping through emotions; thinking is neither contemplation nor meditation; thinking it is not data processing. What thinking does is to ground knowledge, that is produce understanding, and may be either an individual or collective activity. Why thinking should be closely associated with language as both a ontological parsing tool (grammer) and a meaning indicator (words) seems clear enough.
Fr. Pavel Florensky: On Experiencing the Boundary
Extracted from Iconostasis, Introduction
trans. Donald Sheehan and Olga Andrejev, St. Vladimir Seminary Press ©1996
These two worlds - the visible and the invisible - are intimately connected, but there reciprocal differences are so immense that the inescapable question arises: what is their boundry? Their boundary separates them, het, simultaneously, it joins them. How do we understand this boundary?
Here, as in any difficult metaphysical question, the best starting point is always what we already know in ourselves. The life of our own psyche, yes our own soul's life is the truest basis upon which we may learn about this boundary between the two worlds. For within ourselves, life in the visible world alternates with life in the invisible, and thus we experience moments - sometimes brief, sometimes extraordinarily fleeting, sometimes even the tiniest atom of time - when the two worlds grow so very near in us that we can see their intimate touching. At such fleeting moments in us, the veil of visibility is torn apart, and through that tear – that break we are still conscious of at that moment – we can sense that the invisible world (still unearthly, still invisible) is breathing: and that both this and another world are dissolving into each other. Our life in such moments becomes an unceasing stream in the same way that air when warmed streams upward in the heat.
Stichera for Vespers, First Saturday in Great Lent
from the Triodion
trans. Seraphim Nassar, Divine Prayers and Services of the Catholic Orthodox Church of Christ
The grace of truth hath shone, and the things which were foreshadowed of old have now been fulfilled openly; for behold, the Church hath put on the incarnate likeness of Christ, a world-transcending adornment, in accordance with the foresign of the tabernacle of the Covenant, that, keeping the Icon of him whom we worship and revere, we may not go astray. Let those, therefore, who believe not thus be robed with confusion; for our kneeling in true worship (not deifying the Icon) of the Incarnate is a glory to us. Let us, therefore, embrace it, O believers, crying, Save O God, thy people and bless thine inheritance..
Stichera for Lauds, Sunday of Orthodoxy
from the Triodion
trans. Seraphim Nassar, Divine Prayers and Services of the Catholic Orthodox Church of Christ
Thy Church, O Lover of mankind, rejoiceth in thee, O thou her Bridegroom and her Creator, who by thy will, as becoming God, didst rescue her from the worship of idols, and joined her to thee by thy precious blood, enjoying the elevation of the noble Icons. Wherefore, she praiseth thee in faith, glorifying thee in joy
We handle the likeness of Thy body and embrace it in consideration of its Source, making plain the mystery of thy dispensation, O Lord, Lover of mankind; for thou didst not appear unto us in delusion or imagination, as claim the followers of Mani, those contenders against God, but in truth and in nature of the body by which we ascend to thy divine longing and love.
Today hath appeared, a day full of joy, because the splendor of true doctrine shineth forth brilliantly, and the Church of Christ no sparkleth, adorned by the elevation of the Icons of the saints and their illustrating pictures, and believers attain there a unity rewarded of God
Gospel of John 1:46-51 (NKJV)
Read at Liturgy on the Sunday of Orthodoxy
And Nathanael said to him "Can anything good come out of Nazareth. Philip said to him, "Come and see." Jesus saw Nathanael coming toward Him and said of him "Behold, an Israelite indeed, in whom there is no deceit." Nathanael said to Him, "How do You know me?" Jesus answered and said to him "Before Philip called you, when you were under the fig tree, I saw you." Nathanael answered and said to Him, "Rabbi, You are the Son of God! You are the King of Israel!" Jesus answered and said to him "Because I said to you "I saw you under the fig tree, do you believe? You will see greater things than these" And He said to him "Most assuredly, I say to you, hereafter you shall see heaven open, and the angels of God ascending and descending upon the Son of Man.