In discussing certain scientific topics, despite the best of intentions, people cannot reach agreement. Intelligent honest people interpret the same data differently, they sometimes have different data from each other, and because of the theoretical commitments they make, they are blind to certain facts. In these situations there is little to be done but to have open debate, to formulate the respective theories in as clear a manner as possible, and to decide where theoretical commitments lie and where there are differences of fact. Once this is done it may be possible to determine what experimental and empirical data can decide these matters. But underdetermination being what it is it is not typically possible to have a demonstrative proof that a particular theory is correct and its rival is incorrect. In practical situations underdetermination is not a problem, established scientific theories, like for example, the theory of evolution have such massive predictive and explanatory power over their rivals that they don’t have realistic rivals.
In some cases when theorists do not agree with each other both sides may feel that the evidence clearly favours their theory. They may feel that their theory is more consistent with known facts, that their theory makes more accurate predictions, etc. In this case the temptation is to accuse the person you disagree with of having some ideological commitment which blinds them to the obvious facts. This conspiracy theory approach is quiet common in the history of academic discourse. Historically when Marx’s theories were criticised it was pointed out that those criticising Marx probably had some material interest they were trying to defend, so their criticisms could be dismissed on those grounds. Freudian’s likewise sometimes responded to criticisms of psychoanalysis by psychoanalyzing the critics of Freud. The critic of Freud was analysed as having issues with authority figures stemming from childhood experiences. With the supposed motive of the critic of psychoanalysis exposed the criticisms could be dismissed. When critics of Behaviourism complained about the method they were interpreted being closet Cartesians who desperately wanted the soul to exist. Obviously not all Behaviourists, Marxists, and Psychoanalysts behaved in this manner, but a lot of them did use this approach and unfortunately it did stifle legitimate criticism of the various disciplines.
Of late I have noted this manner of dealing with disagreement has emerged in evolutionary psychology. So, for example, in evolutionary psychology forums when various issues are discussed, people are quiet frequently accused of adopting a particular position because of some supposed psychological motivation. So if a person mentions something to do with sexual harassment they are accused of unconsciously signalling to potential mates that they are nice guys. Or if people are debating about the degree to which humans are innately violent or innately cooperative they will be accused of doing so because of unconscious political motivations. Thus if a person thinks that the evidence shows that humans are by nature more cooperative than violent (obviously I am simplifying here) they are accused of defending a Rousseau view of human nature, and of being a left wing extremist who is denying obvious fact to support a political belief. On the other hand if a person thinks that the evidence supports violence as opposed to cooperation being dominant they will be accused of doing so because they are Hobbes supporter who are defending a right wing world view despite the obvious facts. In these various debates mountains of evidence is presented by both sides of the debate. However quiet a lot people don’t read the counter evidence and merely attack the motivations of the person presenting the evidence.
What is strange in all of this questioning of people’s motivations is the fact that we all have motivations (some of which we are not aware of), we are subject to unconscious biases, blind spots etc. As human beings we need to be constantly aware of the fact that we do not reason perfectly, hence the importance of empirical checks on our theories, and clear rational debate with those we disagree with. When we dismiss those we disagree with as being ideologically motivated and think that this is justification for ignoring the data they present we forego the possibility of learning.
It is a simple logical point that it is a fallacy to assume that the origin and motivation a person’s reasons determine the truth or falsity of the reasons the person presents. It may be possible to tell a Freudian or Marxist or Evolutionary Psychology story about some unconscious motivation for me believing that X is true. But my motivation is strictly speaking irrelevant to the evidence I present. The evidence is good or bad evidence and should be judged on its own merits. This is a truism that all first year philosophy students are aware of. Yet this truism is constantly flouted when people have disagreements particularly in areas to do with human nature.
I myself have been just of guilty of questioning the motives of those I disagree with, and engaging in ad-hominem attacks. But I think that this approach is seriously misguided. Focusing on the evidence, is what is important, not ad-hominem attacks on those who disagree with one. You may not always be able to convince others that you are correct, and may learn that despite what you thought the evidence doesn’t support your position (this should be a good thing). But if you use a person’s supposed questionable motives as an excuse to ignore data you are no longer playing the game of science.