The root of Teshuvah is that God enlightens his eyes so that his sins become as merits, that is, that he become cognizant and understands that all of his sins were also God's will, (prooftext from the Gemara in Brachot 32b), etc., and like the meaning [, i.e., the resolution of the conflict between God's] knowledge and [human] choice, that the Ariza"l explained at the end of his book 'Arba Me'ot Shekel Kesef' that they are both true (emet), each in a place by itself. In the place where there is choice, there is no place for knowledge, and in the place where there is knowledge, there, in truth, is no choice...
R' Tzadok is saying - and attributing to the Ariza"l - that the age-old contradiction between God's foreknowledge and human free choice doesn't exist. Each one of those represents a paradigm for looking at the world. One cannot operate in both paradigms simultaneously. The contradiction, in that case, is real. But each can provide a fundamentally consistent paradigm for us, as humans, to operate and relate to God. The process of Teshuvah, according to R' Tzadok, is the process by which one shifts from the paradigm of 'choice' to the paradigm of 'knowledge'. In the former perception, sin is the result of human choice - poor choice- for which he bears responsibility. In the knowledge paradigm, there is no choice; all is from God, all is in God, all is known by God, and all is God's will. There's simply no room for human choice. If one can acheive that degree of perception - really, really look at the world in that way - then his sins will have been transformed to be from the same 'stuff' - God's will - as his merits.
The question that bugged me for years (literally) was - which of these is true? It seems that R' Tzadok is saying that really there's no such thing as sin, once one realizes the truth that all is God's will! This whole free-choice thing is just a dumb illusion!
The answer that I've found (and confirmed w/ some folks w/ real bona fides) is this:
R' Zadok is saying that the 'knowledge' paradigm is higher and more difficult to attain than the 'choice' paradigm. But NEITHER represents 'absolute truth'. How does God view it? How is the conflict between knowledge and choice resolved in God's mind, as it were? WE DON'T KNOW and WE CAN'T KNOW, and it's really pretty useless to ask the question. We can know this - free choice is real and true. So is Divine foreknowledge. But not at the same time in the same mind.
To use the terminology of the last post, yediah and bechirah, as we relate to them, are phenomena, and as such, are contingent upon the world of perception that I construct for myself. By shifting perceptual paradigms, I've opened myself up to an entirely new set of phenomena. God's Mind is the Noumenon - the way it REALLY, absolutely, truly is. And we have absolutely no accesss to understanding it as such. We can try to understand God's mind from within our own (and attribute to it things like incomplete or complete foreknowledge), but ought to be humble (and sane) enough to recognize that we haven't TRULY been granted access to God's Mind.
Does that make things clearer, Godol?