There's a subtle difference here. The true scientist strives to be impartial and attempts to learn whether his theory is supported by reasoning and his observations of the universe. Even if he is in love with his theory, if its integration into science would make him rich and famous, he still respects the scientific method. This means that he devotes a large part of his effort to trying to disprove his own theory. He knows that no scientific theory can be proven true, it can only have its probability of being false steadily lowered as it becomes integrated with all other theories, until it becomes "true beyond a reasonable doubt." His quest is to find all the evidence that might disprove his theory and make sure it is not valid. The crackpot is most often driven by his love for his theory, his fantasy of being a populist hero, and/or his subversion of the scientific method to the superstitions and irrationalities of his religion. In the worst case he attempts to prove his theory true, which is something that only happens in math, not science. In religiously-inspired cases he concentrates on proving competing theories false, but he ignores one step in the scientific method: extraordinary assertions require extraordinary substantiation. (For example, the extraordinary assertion that a century and a quarter of ever-more sophisticated evidence consistent with the theory of evolution is wrong requires more evidence than a couple of dubious fossils and a passage in a book of fairytales, before we are required to take it seriously.) The crackpot has no respect at all for another step in the scientific method: peer review. He is convinced that all scientists are part of a conspiracy to silence the hard-working crackpots, because the truth of the crackpottery will somehow put them out of work instead of giving them more work to do, so the rejection of every scientist whose ear he can bend simply strengthens his conviction that he is right. It's okay to use your imagination to lead to possibilities. It's not okay to be blinded by it so that you lose your scientific objectivity and fail to observe the scientific method.