For an introduction let me just say that in Tractate Pesachim chapter 2 we find Rabbi Abahu says when it says in the Torah not to eat something, it is implied not to derive pleasure from it.
The Talmud brings a question on this from trumah [the 2% of ones crops that goes to the priests] that a person can use to change his position on Shabat. [On Shabat you can't go out of 2000 yards. But you can put a meal at a distance from where you are currently at, and then the place of the meal will be considered your place on Shabat.]
Trumah is good for that even though you can't eat it.
The answer the Talmud gives to this is you can undo trumah. It is like an oath that three people can loosen. I asked on this.
I asked --"But not every neder [oath] can be loosened?"
I was thinking of things like you find in tractate Nedarim chapter 9 like nolad [a new situation arises].
He opened up a Rambam and showed me where the Rambam says that we do not open up a permission, but still if the person has regret, three people can permit any neder [commitment].
And to think that just before that I was criticizing him that his anti science world view was in direct contradiction to Maimonides and Saadia Geon. I told him that his world view was based on later Hasidim that rejected the Rambam's world view. I was complaining that he did not learn the Guide For The Perplexed or the Emunot and Deot of Saadia Geon.
My point was that by his learning Hasidic books that gave him a world view that is not just contradictory to that of that of Maimonides, but also that it gives him a world view such that if someone tells him some idea from Maimonides or Saadia Geon, he considers it to be heresy.
The irony here is that I proved my own point. I had formed my ideas about oaths on the Talmud in Nedarim, but never had spent much time learning the laws of Nedarim in the Rambam. So when I heard a view from contrary to my views which I had in fact based on the Talmud, I thought it was completely wrong.
The moral of the story is there is no substitute for learning all the works of the Rambam from the beginning to the end--every last word.--starting from the Guide for the Perplexed. P.S. David Hartman gives a good introduction to the Rambam.
I saw his book in the library of Hebrew University in Jerusalem where I used to hang out.
And I think I should mention that the Guide of the Rambam by itself is hard to swallow. It does not have magnetic pull . Still I think it is important because without it it is too easy to come up with alternative world views that are opposite to the Torah and yet still to be thinking they are Torah. When the Rambam writes his book for confused people he does not mean just people that know they are confused but especially people that don't think they are confused but think they know the worldview of the Torah better than the Rambam.