Problems with using criteria for casual inference

(Adapted from "Epidemiology, An Introduction", Kenneth Rothman, 2002)

Criterion	Problems with the Criterion
Strength	Strength depends on the prevalence of other causes of disease present in the population, and therefore is not a biologic characteristic.
Consistency	There are plausible reasons for not seeing consistent results, and these exceptions are best seen with hindsight.
Specificity	A cause can have many effects.
Temporality	Although this is thought to be the only true causal criterion, it can be difficult to establish.
Biologic gradient	A relationship between and exposure and outcome that has a threshold would not show a progressive effect.
Plausibility	Too subjective.
Coherence	Vague and very similar to plausibility.
Experimental evidence	Not always available or feasible.
Analogy	Analogies abound.