I'd like to better define cause and effect in engineering terms so I thought what better place to start than finite element analysis (FEA)… ok, strange you may say. But here's the idea. In FEA, one might say that each element is acted upon by some kind of 'causal action' which affects the element depending on its material properties. The book, "What Every Engineer Should Know About Finite Element Analysis", edited by John Brauer, separates FEA into the following types: 1. Structural Analysis 2. Thermal Analysis 3. Electromagnetic Analysis 4. Fluid Analysis In each case, Brauer examines a field and says, "each field has a different influence on device performance." and then points out the field for each "potential". Note that in the list below, each first term is a field and each second term is a potential and is written "Field" / "Potential" such that Heat Flux is a field and Temperature is a potential. From Table 2.1 in this book: Heat Flux / Temperature Mechanical Stress / Displacement Electric Field / Voltage Magnetic Field / Magnetic vector potential Fluid Velocity / Fluid Potential The concept of a field and a potential operating at any point within the model gives us a starting point in defining a causal action. Each field is in a sense a "causal action". Heat flux is the flow of thermal energy and Brauer is suggesting it is 'driven' by a potential. Of course, the potential AT ANY SINGLE POINT is what is driving this heat flux, so we might also recognize that temperature potential is a local causal effect in the sense that heat flux is driven by the local temperature differential, not by a temperature differential some distance away. Here, the causal action might be considered to be the heat flux with the effect being an affect on the temperature at some point. How the temperature at some point is affected is of course dependant on the material property. In this case the properties include thermal conductivity and heat capacity among other properties. Similarly, mechanical stress can be thought of as causal action with the effect being the displacement each element experiences. In each case, it seems to me the "field" is what causes a change, and the effect is what is being called the potential which exists across the entire model and is dependant on material properties. To me, this makes more sense than reversing the two and suggesting the potential is the cause and the field is the affect. Regardless, what do you think is a cause and which is an effect, or perhaps you don't think it matters?