 (Martin’s own modified causal principle is more complicated than this in allowing for indeterministic causation. We gloss over this important complication here). Take N to be the fundamental kind which characterizes a veridical experience of a snow-covered churchyard, according to the naive realist. Does Causal Principle 2 allow us to say that N is present in the causally matching hallucinatory case, as (CKA) predicts? No. For the hallucination is produced in circumstances that differ in non-causal conditions necessary for the occurrence of N given how the naive realist understands N: in the circumstances in which the hallucination occurs there is no appropriate object of perception, but the presence of such an object is necessary for the occurrence of N.