Passage 1
It is but a very small part of the entire process, which goes to form a piece of reasoning, which they are capable of performing. For, if we begin from the beginning, that process would involve four tolerably distinct steps. There is, first, the statement of our data in accurate logical language. This step deserves to be reckoned, since the variations of popular language are so multitudinous, and often so vague and ambiguous, that they may need careful consideration before they can be reduced to form. Then, secondly, we have to throw these statements into a form fit for the engine to work with — in this case the reduction of each proposition to its elementary denials. [...] Thirdly, there is the combination or further treatment of our premises after such reduction. Finally, the results have to be interpreted or read off. This last generally gives rise to much opening for skill and sagacity; [...] it then becomes a question of judgment which of these is the simplest and best. [...] I cannot see that any machine can hope to help us except in the third of these steps; so that it seems very doubtful whether any thing of this sort really deserves the name of a logical engine.
Tools and agentsCognition, attention, and judgmentcalculation is insufficient · advancesselection and judgment · advanceslimited servant · advancesLogic, language, and formal reasoningMeaning, experience, and interpretationNo judgment offeredIndividualMachine or artificial systemMind and body
Venn separates reasoning into problem formulation, machine preparation, formal combination, and interpretation. He limits machinery to the third step; exact language and interpretive choice remain human work.
Symbolic Logic (1881), ch. V, pp. 119–121