The goal of any elegant conceptualization is to render a problem retroactively obvious. 

The only remnant of nonobviousness that remains is the record of the struggle  to understand without the benefit of the now-obvious concept. Once this struggle terminates with the acquisition of a concept it is impossible to recover an immediate sense of the problem (its problematic essence) because the concept has become intrinsic to the consciousness that remembers the problem. 

When the solution is found, the problem is lost. 

But the loss is normally undetected, because concept insinutes itself into the recollection of the problem, imperceptibly rescuing the mind before it can need rescue. 

What makes this strange insinuation of concept imperceptible is this: concepts are tacit. We confuse the articulate thoughts we have under the guidance of concepts with the concepts themselves, when in fact the articulations are verbal concatenations (to use Adam Miller’s perfect term) that require the guidance of the tacit concept itself to function conceptually. (Michael Polanyi calls this the “tacit coefficient”). If you do not understand what I mean by this, stop now and note: what is missing at this exact moment is the tacit conceptual guidance required to understand the meaning of these words. Without this tacit guidance, the articulation is entirely useless, and will remain so until the proper tacit concept animates it. 

The concept does not need any articulation to function. Once a concept is conceived it lives and operates in the movements of the mind, priducing understandings, and can do this unaided by articulation indefinitely. 

Most of us are not used to thinking of thought in this way. If we cannot articulate a concept we use we are accustomed to attributing that concept to reality itself: it is just self-evidently out there in the world to see. But the concept is in us, and is us, shaping our perceptions, our actions, our thoughless reactions, our dreams — and our memories of the past, even the memories preceding the conception.

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A concept is unforgettable because it is immemorable. A concept is not remembered, because it is who does the remembering. Just as sight sees without being seen, concepts conceive without being conceived. 

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A resolved problem can no longer be experienced as problematic. Since the problematic character of a problem is its very essence, a problem is irrecoverable once resolved.