Reliability

I was reading in my European history book and there was a significantly large section on Freud. The most interesting line was this, at the very end of the section on Freud: "Although many of Freud's ideas have been shown to be wrong in many details, he is still regarded as an important figure because of the impact his theories have had" (Spielvogel, 676). So, Freud is not completely right about everything. Is it now we can label him as useless or irrelevant to today? I did not know when I first read that statement. My teacher assigned a primary source document, one of Freud's lectures on psychoanalysis. A small portion of it reads:

"I found confirmation of the fact that the forgotten memories were not lost. They were in the patient's possession and were rady to emerge in association to what still known by him; but there was some force that prevented them from being conscious and compelled them to remain unconscious. The existence of this force could be assumed with certainty, since one became aware of an effort corresponding to it if, in opposition to it, one tried to introduce the unconscious memories into the patient's consciousness" (Freud qtd. in Spielvogel, 675).

This is quite a bit to take in. Freud is simply trying to say that when he could not get the information he was "seeking" (that is, the forgotten memories or latent content of dreams), he assumed they existed, but were being repressed. Frankly, I find faults in Freud. Here is my logic: How could he have known about "forgotten" memories if they were unknown until his psychoanalysis? If he was unable to reach those memories/content, how could he have known they existed? In short, how can you look for something that you don't even know exists? Second, he says that one can assume that repressive forces exist. Unfortunately, there needs to be cold, hard evidence for this. I don't know, I seem to have a problem with Freud's thinking, others might not. Still, I wonder, because mostly everything I have read in Freud's text had made sense (or partial sense) up till now. Now, I'm beginning to wonder. Is Freud a reliable source? He is a bit outdated, like about 100 years outdated.