In Towards a Theory of Ignorance, I adumbrated a theoretical account of human ignorance. I argued that a theory of ignorance is important, especially for a forward-looking movement like transhumanism, because of such phenomena as: the extraordinary growth of science since its Baconian origin in the seventeenth century; the fractal-like phenomenon of disciplinary and vocational specialization; the "breadth-depth trade-off" that constrains individual human knowledge; etc. Together, these phenomena might lead one to posit a kind of Malthusian principle concerning the epistemic relationship between the collective group and individual person. Such a principle might be: The knowledge had by the individual grows at an arithmetical rate, while the knowledge had by the collective grows at a geometric rate. The result is an exponential divergence between the group's knowledge and the person's knowledge. As Langdon Winner writes: "If ignorance is measured by the amount of available knowledge that an individual or collective 'knower' does not comprehend, one must admit that ignorance, that is relative ignorance, is growing." Finally, I suggested (following Mark Walker) that such phenomena together constitute a good premise for arguing that we ought to develop a species of cognitively "enhanced" posthumans, who would thus be more "mentally equipped" to understand, mitigate and control the negative externalities--most notably the existential risks--that result from our technological progeny.
There are at least two additional issues that are relevant to a theory of ignorance, but which I did not mention. I discuss these briefly below:
(1) In his The Mystery of Being, Gabriel Marcel distinguishes between a problem and a mystery. As the Princeton theologian Daniel Migliore puts it: "While a problem can be solved, a mystery is inexhaustible. A problem can be held at arm's length; a mystery encompasses us and will not let us keep a safe distance." This, of course, ties into our prior discussion of Nicholas of Cusa and "apophatic" theology: God is an incomprehensible mystery, definable only through negation--that is, by what He's not. Furthermore, the more one understands his or her deep and ineradicable ignorance about God, the more "learned" he or she becomes. This is Cusa's "doctrine of learned ignorance." Thus, the boundary between problems and mysteries marks the absolute limits of human knowledge: what lies before this boundary is in principle solvable, even if not yet solved; and what lies beyond it is in principle unsolvable, or completely inscrutable to begin with.
But the distinction between problems and mysteries is not found only in theology. Indeed, the linguist and polymath Noam Chomsky has championed a view of human mental limitations called "cognitive closure." (Note: one finds the same basic position in other works, such as Jerry Fodor's 2000 book, under the name "epistemic boundedness.") On this account, humans are in principle "cognitively closed" to mysteries, while problems are in principle epistemically accessible (that is, 'mystery' and 'problem' are defined as such). For example, the conundra of free will and consciousness are, according to Chomsky, both mysteries. Along these lines, a group of philosophers of mind have espoused a position called New Mysterianism, which states that humans will never fully understand the subjective or phenomenal aspect of consciousness (what Ned Block calls P-consciousness, as opposed to A-consciousness). This feature of conscious thought is often called qualia. Put differently, the connection between, or identity of, mind and matter is like that of mass and energy before 1905 (e.g., "uttered by a pre-Socratic philosopher"), except that the breakthrough paper connecting the two will never be published. That is what New Mysterianists claim.
Furthermore, as Daniel Dennett writes, Chomsky apparently sees the language organ as "not an adaptation, but... a mystery, or a hopeful monster." Thus, Darwin has nothing to say about the evolutionary emergence of human natural languages. Dennett adds that the cognitive closure "argument is presented as a biological, naturalistic argument, reminding us of our kinship with the other beasts, and warning us not to fall into the ancient trap of thinking 'how like an angel' we human 'souls' are with out 'infinite' minds." Thus, the philosopher Colin McGinn writes that "what is closed to the mind of a rat may be open to the mind of a monkey, and what is open to us may be closed to the monkey." Interestingly, this seems to gesture at the evolution-based cognitive metaphorology of George Lakoff and Mark Johnson, who argue that humans have evolved conceptual mapping mechanisms for understanding more abstract domains of thought/experience in terms of more concrete ones. In other words, human cognition is highly limited--our only way to make sense of, for example, the emotion of love is in terms of more familiar activities like journeys. Thus, LOVE IS A JOURNEY, which yields linguistic expressions like "Look how far we've come," "It's been a long, bumpy road," "We're at a crossroads," etc.
Now, the problem-mystery distinction is of interest to transhumanism because the creation of superintelligent beings--either machines that can think or technologically "enhanced" human beings--would almost certainly redefine the boundaries between problems and mysteries, between those questions that are in principle answerable and those questions that we cannot even ask. Thus, not only would the development of a posthuman species have practical benefits (presumably in terms of reducing the probability of an existential disaster, for example), but it would also likely lead to the discovery and elucidation of arcana by which modern Homo sapiens cannot even be baffled, due to our ineluctable epistemic boundedness. Along these lines, Nick Bostrom has even suggested (although the citation eludes me at the moment) that his academic focus is primarily on futurological rather than philosophical matters because, once we create superintelligent machines, many of the persistent puzzles of philosophy will be quickly solved. (See this paper for more.)
(2) The second issue worth mentioning is sometimes called "the theory of rational ignorance," or simply rational ignorance. The idea here is that, given the increasingly complex informational environment enveloping the modern individual, it is sometimes rational to be ignorant about an issue X. That is to say, if the payoff of knowing about X is not worth the commitments required to learn about X, then it might be rational to be X-ignorant. (This can be understood, I believe, as either a normative or descriptive theory: we ought to be ignorant about certain things, given our "finitary predicament," in contrast to "people often rationally choose to remain ignorant of a topic because the perceived utility value of the knowledge is low or even negative," respectively.) As I understand it, rational ignorance is discussed in economics--specifically in public choice theory. Sadly (and indeed ironically) I am not qualified to discuss this theory in detail. Thus, the second point must end here--it's a point worth noting, but one not well understood by the author.
In sum, then, a comprehensive theory of ignorance would account for not only the explananda discussed in the original post (some of which are listed above), but also (1) the relation between both humans and posthumans to the problem-mystery distinction championed by luminaries like Chomsky, and (2) the rationality of remaining ignorant about specific issues, especially given the Malthusian principle of epistemic growth explicated in the first paragraph.