Exposition: The Post Hoc Fallacy is committed whenever one reasons to a causal conclusion based solely on the supposed cause preceding its effect. Of course, it is a necessary condition of causation that the cause precede the effect, but it is not a sufficient condition. Thus, post hoc evidence may suggest the hypothesis of a causal relationship, which then requires further testing, but it is never sufficient evidence on its own.
Simply make a cup of soap nut 'tea' by soaking 4 or 5 bagged soap nuts in a cup of very hot water for approximately 3 minutes. Pour both the soap nuts liquid and bag in wash. Remove from washer at end of the wash to dry (leave soap nuts in bag). Re-use 3 to 5 times. Soap nuts are no longer effective when they thin, turn soft, mushy and very light tan or gray.
Hair and Nails. I'm sure you recognize Lather, Rinse, Repeat as the infamous and widely misunderstood directions on the back of the shampoo bottle. I've often wondered why the directions are so elusive, and can only imagine that those who haven't sat in a class about proper shampooing must be even more confused.