Sentence:  Presumably , if the reverse <WSD>is</WSD> the case and the good effect is more certain than the evil result that may be forthcoming , not only must the good and the evil be prudentially weighed and found proportionate , but also calculation of the probabilities and of the degree of certainty or uncertainty in the good or evil effect must be taken into account . 
Meaning of the word marked with <WSD> tags:  be identical to; be someone or something