Brains are organs that organize experience, look for patterns and meaning, and try to create predictions for the purpose of optimizing future experience. Yes, I know. That sounds rather academic. The point is, experience comes to us disorganized, confusing, nonstop, and overwhelmingly complex. What we do in order to manage it is to try to organize it. Over time, people develop systems of thought which are shorthand ways of organizing that experience. For example, physics is a system of thought that explains the set-up of the material world. We have planets, and atoms, and waves, and sounds. Physics organizes those experiences by describing them and creating categories of patterns so that we can understand them in relation to each other and in relation to other things.
Marxism is a system of thought. So are religions. So are political systems. So are philosophies and child rearing methods. They are different ways of organizing our experience and understanding it so that we can figure out what we want to do and how we feel about it. Some systems of thought seem helpful to us or they seem to correspond more closely to what we think is real outside of ourselves. We adopt systems of thought, study them, and make them part of our identity. I am a democrat, we say, and we mean something specific by that.
Systems of thought are not absolutely arbitrary. They need to correspond more or less to our real experience in the world. They need to be helpful to us in coping with problems and in building our lives. If they are not somewhat real and useful, they will not survive and be used.
What happens, though, is that we begin to forget that our systems of thought are ways we are organizing our experience, and they begin to feel like some transcendent reality that we can know for sure. We really would like to be sure about things. Of course we believe our system of thought is better than other systems. That is why we chose it, or were taught it. And we can see by experience over time that some ways of looking at the world and living in it are better than other ways.
What happens over time, though, is that the system of thought itself becomes the object of our conviction, and we are no longer open to questions about our experience. We become loyal to a way of understanding rather than to the goal of moving toward greater understanding. We do not want to continue to be challenged and reflective. It is easier to be certain and relax in the assurance of being right.
Systems of thought are tools. They can be helpful and constructive. Tools do not carry a super-ordinate reality. They are a means of accomplishing something else. We live in an uncertain and unpredictable world, and we need to be able to make choices and plan for the future. Systems of thought can operate to help us create better lives. Or they can limit us and isolate us from a richer, more flexible approach to the complexity of everyday life.