Each transition between kinds of understanding involves a specific friction that cannot be substituted. The friction of somatic-to-mythic translation cannot substitute for the friction of romantic-to-philosophic systematization. A child who has been given extensive physical practice but no exposure to the world's strangeness will have rich somatic tools and impoverished romantic ones. The frictions are not fungible; they cannot be consolidated into a single 'productive struggle' that serves all developmental purposes equally.
This non-fungibility has direct implications for AI deployment in education. The common recommendation — 'preserve productive struggle' — is correct but insufficiently specific. Which productive struggle? At which developmental level? For which cognitive tools? The struggle of writing code by hand develops somatic and philosophic understanding of computational logic; the struggle of formulating a research question develops philosophic and ironic understanding of one's own knowledge gaps. AI might appropriately eliminate the first while it must preserve the second.
The parallel to Segal's concept of ascending friction in the professional context is precise. In the professional context, AI removes implementation friction and exposes the harder friction of judgment — what to build and why. In the developmental context, AI's removal of information friction should expose the harder friction of understanding — what knowledge means, how frameworks relate, what the limits of one's own comprehension are. This happens only if the educational environment is designed to preserve the harder friction rather than smooth it away alongside the easier kind.
The principle emerges across Egan's work but is most explicitly articulated in his discussions of how cognitive tools develop at each stage of the sequence.
It connects to a broader tradition including Dewey's account of problematic situations, Vygotsky's zone of proximal development, and contemporary research on desirable difficulties in learning (Bjork and Bjork).
Difficulty is mechanism, not cost. The struggle is how the cognitive tools are built.
Frictions are not fungible. The specific kinds of struggle at each stage cannot substitute for one another.
AI's two effects. Technology can eliminate mechanical friction (gain) or developmental friction (loss).
Distinction requires theory. Separating productive from unproductive friction requires a developmental framework.
Ascending in development too. AI's elimination of easier frictions should expose harder developmental frictions, but only with pedagogical intention.