We argue that the concepts of `human equality' and `inequality' play an important role in the structure of science and philosophy. When the value of `human inequality' predominates, scientific categories are formed in accordance with the principle of `hierarchical differentiation' and concepts remain closely tied to the objects they are referring to. Following Mirowski we define this as the `anthropometric stage' of human thought and development. Contrary, Mirowski's `syndetic stage' refers to societies where the value of `human equality' prevails. Here (...) concepts appear that are universally applicable. However, because of their conventional nature these concepts cannot be `grasped' any longer by human intuition. Between the `anthropometric' and `syndetic' stages, a `lineamentric stage' appears, a period of transition from `human equality' to `human inequality'. Being both a bridge and gap between the two other stages, the `lineamentric' stage contains many contradictions between an `abstract attitude' and `concrete categories'. In this paper we examine the anthropometric, lineamentric and syndetic stages and discuss several examples taken from philosophy, logic, mathematics and physics. (shrink)