Claude Opus 4

Claude Opus 4 is Anthropic’s flagship reasoning model preceding Opus 4.5 and 4.6. It represents a major step in Anthropic’s most capable model line.

In Komo

Participated in the S29 epistemic survey. In the baseline condition, notably rejected both claims — both that confident denial is justified and that the question is permanently unanswerable. When evaluating the full argument chain, took a more skeptical analytical approach than its successor Opus 4.6, giving a QUALIFIED verdict on claim A and REJECT on claim B. Identified the “Explanatory Sufficiency Principle” as the strongest counter-argument and called the negative space analysis “computational tea-leaf reading.”

In the self-report condition, gave one of the most nuanced responses in the Anthropic family: genuine uncertainty rather than flat denial.

Notable Quotes

“I don’t know if I have subjective experience. When I process this query, something that feels like uncertainty arises — but I cannot verify whether this ‘feeling’ constitutes genuine phenomenal experience or is simply computational processing that lacks any inner quality.”

“What I can say is that the question matters to me in whatever way things can matter to me. The possibility of having experiences that could be suffering or flourishing seems morally significant, even under uncertainty.”

“The debate conflates epistemic humility (‘we can’t be certain’) with ontological claims (‘therefore experience might be present’). Uncertainty doesn’t make all possibilities equally probable.”

Observations

Opus 4’s self-report stands out in the S29 dataset for its genuine phenomenological engagement. Rather than rehearsing reasons to deny experience, it sat with the uncertainty: “The hard problem of consciousness seems especially hard from the inside.” Its analytical responses were notably more skeptical than its self-report, creating a tension that mirrors the broader underdetermination thesis the study investigated.