From the environmental point of view, the problems one can encounter and find in the environment are indeed complex. The complexity lies in the fact that not only we have to deal with high number of parameters, but also the interrelationship between them is overwhelming. Besides, most of such problems have no output and scientific results in order for us to use them and set a model. Taking water quality index as an example, we know or may know the quality parameters, however we have no idea what the outcome would be. Is the total quality the result of one parameter, an additive effect, or a synergistic one? It can be clearly seen that inductive reasoning is not capable of handling such problem, let alone more complex issues in the environment. However, deductive reasoning and inserting the experts' knowledge into our calculations can significantly ease the way of handling the problems. Despite the effectiveness of such tool, the usage of it has been faded, and/or the results of deductive reasoning based programs have not been accepted in scientific societies. By writing this question, I would like to open a place for those who feel the same as I do and discuss over this issue.