Jaap Van Brakel

Models underlying the use of similarity considerations, dimensionless numbers, and dimensional analysis in chemical engineering are discussed. Special attention is given to the many levels at which models and ceteris paribus conditions play a role and to the modeling of initial and boundary conditions. It is shown that both the laws or dimensionless number correlations and the systems to which they apply are models. More generally, no matter which model or description one picks out, what is being modeled is itself a model of something else. Instead of saying that the artifact S models the given B, it is therefore better to say that S and B jointly make up B and S

In this paper my aim is to shed light on the common behavior of human beings by looking at '' first contacts '': the situation where people with unshared histories first meet. The limits of the human life form are given by what is similar in the common behavior of human beings. But what is similar should not be understood as something that is biologically or psychologically or transcendentally shared by all human beings. What is similar is what human beings would recognize as similar in first or other contacts-a similarity that is, in a way, transcendentally grounded, but the content of this grounding remains tied to the local situation of actual encounters. To be a human person, it is both an empirical and a transcendental precondition that one knows the certainties of particular form of life and that one is capable of recognizing and dealing with an indefinite variety of human behaviors. Because I participate in form of life, I can interact with other form of life. By considering first contacts and by interacting with other communities, one can learn to understand better what the common behavior of human beings is/are.