Claim. Hume’s empiricism collapsed into skepticism because it treated causality as merely subjective and recognized only bundles of impressions and ideas — seeing, in Unification Thought terms, only the inner Hyungsang as real.
Elaboration. Hume analyzed the human mind into ideas and held that complex ideas arise by association through three principles: resemblance, contiguity, and cause-and-effect. He took resemblance and contiguity as yielding sure knowledge but reduced causality to subjective belief, denying both material substance and spiritual substance (self) and ending in a skepticism that even imperiled natural science (Hume).
Lee’s response has two prongs. First, causality is not merely subjective — as argued in the epistemology chapter, it is both subjective and objective, grounded in the actual subject-object correlativity of beings. Second, the structural diagnosis: Hume recognized only impressions and ideas, which in Unification Thought terms is only the inner Hyungsang — the content side of the inner mental structure. He did not recognize the inner Sungsang (the functions of intellect, emotion, and will that act upon ideas) nor the subject self that performs the inner give-and-receive action. With only one half of the inner four-position foundation acknowledged, no truth-multiplication is possible, and skepticism is the only consistent terminus.
The further problem is atomism: Hume tried to build a complete philosophy from ‘separate impressions and ideas.’ Without correlativity holding them in subject-object relation, association cannot deliver knowledge — it can only register surface patterns. Cause-and-effect, which precisely encodes correlativity, therefore had to be debunked on Hume’s terms, even though it is the most truth-bearing of the three principles he listed.
Lee’s analysis here anticipates Kant’s response (next atomic): Kant felt Hume’s pressure on causality and tried to rescue objective validity by positing a priori forms in the subject. Lee will argue that Kant got closer but still missed that the subject brings not only forms but content (images) — making the subject side richer than Kant supposed, and the operation a collation rather than a synthesis.
See also. kant-synthesis-as-collation, ut-epistemology-unifies-empiricism-rationalism-marxism-kant, ut-critique-of-kantian-agnosticism-via-sungsang-hyungsang