re: #167 I cannot.

There’s other reasons as well. Say you think company A is the bees knees and company B which is in the same industry sucks. You’re either uncertain of what’s going to happen in the industry over the near term, or even think the it could go into decline. Shorting the stock of company B while buying the stock of company A lets you invest in company A while protecting yourself against a reversal in the industry as a whole.