Vive,
Menger is describing how it’s done, Mises why it’s done. They do not disagree.
As for Jaffe, what he says about man is nothing Mises would disagree with. I don’t see the relevance.
To predict the future and tell people what to do about it seems insane.
Just for the record, the Mises quotes I found on this topic are here. I’ll copy-paste a modified version for your convenience.
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Praxeology, the a priori science of human action, and, more specifically, its up to now best-developed part, economics, provides in its field a consummate interpretation of past events recorded and a consummate anticipation of the effects to be expected from future actions of a definite kind.
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This is the reason why history cannot predict things to come and why it is an illusion to believe that qualitative economics can be replaced or supplemented by quantitative economics. [Meaning that qualitative economics CAN predict stuff].
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The predictions of praxeology are, within the range of their applicability, absolutely certain.
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Economics can predict the effects to be expected from resorting to definite measures of economic policies. It can answer the question whether a definite policy is able to attain the ends aimed at and, if the answer is in the negative, what its real effects will be.
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Economics too can make predictions in the sense in which this ability is attributed to the natural sciences. The economist can and does know in advance what effect an increase in the quantity of money will have upon its purchasing power or what consequences price controls must have. Therefore, the inflations of the age of war and revolution, and the controls enacted in connection with them, brought about no results unforeseen by economics.
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…the public’s interest in the studies labeled as economic is entirely due to the expectation that one can learn something about the methods to be resorted to for the attainment of definite ends. The students attending the courses of the professors of “economics” as well as the governments appointing “economic” advisers are anxious to get information about the future,…
Bottom line, Mises says very clearly that economics [meaning of course Austrian economics, what other kind is there] is great both for accurately predicting the future and prescribing what to do about it.