Off topic but I have always felt this seemed like his misunderstanding rather than theirs. It’s an odd question, but it’s a very sensible point to make if Babbage has just told you this will solve the problem of mistakes in calculations - humans being involved at the start means human error still plagues the output.
> I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.
Well, he did diagnose the situation correctly. He couldn't comprehend the confusion of ideas that provoked the question.
I'm also not entirely sure it's an odd question to ask. To this day, users are surprised when their software produces garbage output instead of failing. Perhaps the members of parliament were expecting some form of input validation or sanity checking out output.
Looking into his biography, it seems that he was indeed pitching the engine not as a means of efficiency, but as a means of avoiding mistakes in mathematical tables. It would have done Babbage well to insist he couldn't possibly solve all classes of mistakes, but would have solved a great many of them! "Why yes Senator, you are quite intelligent and handsome and make a fair point, allow me to give you the finer picture..."
Would have also been a fair point if Babbage had channeled his inner techbro and insisted it would directly replace human calculators; simple machines like Babbage's will chug along blindly on obviously erroneous data, but humans for all their sloppiness can often backtrack on errors.
