Mortimer Adler, in his "How to Read a Book" (1972 edition), Chapter 10, "Criticizing a Book Fairly", wrote:
The third [general maxim of intellectual etiquette] is closely related to the second. It states another condition prior to the undertaking of criticism. It recommends that you regard disagreements as capable of being resolved. Where the second maxim urged you not to disagree disputatiously, this one warns you against disagreeing hopelessly. One is hopeless about the fruitfulness of discussion if he does not recognize that all rational men can agree. Note that we said "can agree." We did not say all rational men do agree. Even when they do not agree, they can. The point we are trying to make is that disagreement is futile agitation unless it is undertaken with the hope that it may lead to the resolution of an issue.
These two facts, that people do disagree and can agree, arise from the complexity of human nature. Men are rational animals. Their rationality is the source of their power to agree. Their animality, and the imperfections of their reason that it entails, is the cause of most of the disagreements that occur. Men are creatures of passion and prejudice. The language they must use to communicate is an imperfect medium, clouded by emotion and colored by interest, as well as inadequately transparent for thought. Yet to the extent that men are rational, these obstacles to their understanding can be overcome. The sort of disagreement that is only apparent, the sort that results from misunderstanding, is certainly curable.
There is, of course, another sort of disagreement, which is owing merely to inequalities of knowledge. The relatively ignorant often wrongly disagree with the relatively learned about matters exceeding their knowledge. The more learned, however, have a right to be critical of errors made by those who lack relevant knowledge. Disagreement of this sort can also be corrected. Inequality of knowledge is always curable by instruction.
There may still be other disagreements that are more deeply buried, and that may subsist in the body of reason itself. It is hard to be sure about these, and almost impossible for reason to describe them. In any event, what we have just said applies to the great majority of disagreements. They can be resolved by the removal of misunderstanding or of ignorance. Both cures are usually possible, though often difficult. Hence the person who, at any stage of a conversation, disagrees, should at least hope to reach agreement in the end. He should be as much prepared to have his own mind changed as seek to change the mind of another. He should always keep before him the possibility that he misunderstands or that he is ignorant on some point. No one who looks upon disagreement as an occasion for teaching another should forget that it is also an occasion for being taught.
I have two questions regarding this passage. I know it is usually recommended to ask one question at a time, but I hope this will be justify for now, because the questions are really very close to each other.
The first question is about the sentence that mentions "disagreements that subsist in the body of reason itself." What this sentence is actually about? Is it about disagreements like the existence of God, for example? Or about whether Picasso's "Portrait of woman in d'hermine pass" ("Olga") is a talented work of art or just a weird and ugly painting of a mediocre and overrated painter? (No offence to Pablo Picasso here. This is not what I think about him or his works myself.) Or maybe about something different/else? I am, of course, asking primarily about the evidences in the book itself.
The second question is about the meaning of the whole passage. The author says that, except for "disagreements that subsist in the body of reason itself," two rational men can always agree if they have enough information and can talk to each other without passion and prejudice. Does it mean that the author shares the view according to which there is no such thing as subjective reality, that is, that in the end there is only one correct answer on moral dilemmas like, for example, death penalty for the most violent criminals, or about scientific questions like, for example, what will happen if you can travel back in time and kill your parents?
