First off, the original text has quite a sum of grammatical errors, so if I were to change it, I would change it to " Many jobs are complicated, funny and life-affirming. Some are simultaneously abstract and cerebral. It makes our minds work hard to under stand the ambiguities, feelings, intellectual ideas, and scientific discoveries that we have made." And to answer the original question, no, you cant change it that way. why? Well, if you look at the third line of the text, it says "makes OUR minds work". By putting "our" in the sentence we are referring to ourselves as a group. Your mistake is that you used, "they", as in referring to another group. lol sorry for the extra info, got a bit carried away there :P