To cut to the chase on this, I would offer Joseph Ratzinger's theological espistemology to offer the prototype of all knowing, i.e., how one knows Jesus Christ. Without doing philosophy as such, Ratzinger is deploying a theological phenomenology with a universal reach since Christ is "the image [icon, not sign] of the the invisible God, the firstborn of all creation, the one in whom the fullness of god was pleased to dwell (Col. 1, 15. 19). Barron goes on: "Lest we miss the power of these statements, theri implications are clarly spelled out: 'In him all things in heaven and earth were created, thisgs visible and invisible, whether thrones of dominions or rulers or powers' (V. 16). In this Jesus, all things have come to be; he is the proitoitype of all finite existence, even of those great powers that transcend the world and govern human affairs...Individuials, societies, cultures, animals, plants, planets and the stars - all will be drawn into an eschatological harmony though him. Mind you, Jesus is not merely the symbol of an intelligibility, coherence, and reconciliation that can exist apart from him; rather, he is the active and indispensable means by wich these realities come to be. This Jesus, in short, is the all-embracing, all-including, all-reconciling Lord of whatever is to be found in the dimensions of time and space" ("The Priority of Christ," ibid. 134-135).
I offer this as prototypical of all knowing because Christ as God-Man is the very center of the created world (See R. Barron's "The Priority of Christ" Brazos (2007) 133-135). In knowing Christ, one has already known creation in its most profound ontological architecture. As Barron says: "to acknowledge the epistemic primacy of Jesus Christ is, first, to assume the intelligibiility of all that is. Since all has been made through, and will be ordered by, a divine rationality, there must be form in all finite being as a whole and in each particular thing that exists; what comes to be through the Logos is, necessarily, logical. This implies, of course, that there is an unavoidable correspondence between the activity of the mind and the structure of being: intelligence will find its fulfillment in this universal and inescapable intelligibility.
In his "Behold the Pierced One," the first two theses have to do with the Person of Jesus Christ - Son/Logos of the Father - as constitutively relational, and, as enfleshed, constantly in prayer. The constancy of prayer is Christ's proper act as man since His Person is Son and therefore pure relation to the Father. Thesis three draws out the logical consequence: if the "to be" of Christ is prayer, and the truth of knowing follows on the conformity of the mind with reality (that is the Person of Christ) - which translates that "like is known by like" - then, Christ can only be known by the act of prayer - which is the going out of self (Lk. 9, 18). In the act of prayer (whatever is action-for other), one experiences going out of self. That is, one is the process of becoming (asymptotically) "another Christ." By the experience of self ab intus (as "other Christ"), one knows Christ by knowing oneselfm and can say: "You are the Christ, the son of the living God" )Mt. 16, 16). This, now, coheres with Ratzinger's work on the meaning of revelation as taking place in the act of faith as the act of self-transcendence. Christ is the revelation of the Father (sacred scripture is the residue of the Person and actions of Christ - not the revelation), and that revelation only takes place where this transformation into Christ takes place. Barron calls this the "Christ-Mind" ('The Priorty of Christ," chpt 10) It is the mind of the experience of the self as "other Christ" which sees everything in relation: "This implies that the primordial intelligibility is a "being-with-the-other, or better, a being-in-the -other, a coinherence... Therefore relationality, being-for-the-other, must be the form that, at the deepest level, conditions whatever is and the truth that satisfies the hunger of the mind. It is not simply reasonability that characterizes the real, but this type of reasonability" ("The Priority of Christ" ibid. p. 155).