In Freud’s Interpretation of Dreams, he is trying to interpret the meaning of a particular dream he had. He begins by saying that he wrote the dream down as soon as he woke up, and the analysis is a play-by-play breakdown of the events. While he does a thorough job of analyzing the possible meanings of his dream, he assumes that there is some meaning behind it, “If we adopt the method of interpreting dreams which I have indicated here, we shall find that dreams really have a meaning and are far from being the expression of a fragmentary activity of the brain, as the authorities have claimed.”
This is a pretty bold statement, especially considering that he has not yet proved his claim. While it is a valid scientific exploration into whether or not dreams have meaning, Freud is operating under the assumption that dreams definitively have some sort of meaning, and goes so far as to question the validity of the conclusions of the larger scientific community at the time. Why is this a problematic approach to researching dreams in a scientific context, and how would this affect the eventual conclusions of his research if he was already convinced he was right?