you mostly think of functions in terms of energy. like modules. switching modules or the route of information flow from module to module seems to be something that should be considered. i agree. in the world of energy flow people change their momentary configuration all the time. which creates different results. but from a perspective of evaluating the contents of the resulting intelligence, these results have a different quality. this can easily be observed. i will later write about how that comes about. and strictly from an simple darwinistic perspective, it seems desirable that the highest overall quality is preferred most of the time. individuals should also adapt to situation, but in a society the quality of an individuals result will determine the social situation that manifests, so most of the time, choosing the configuration of functions, which brings about the highest quality, will be more desirable than adapting the configuration to meet external requirements. if you understand functions in terms of their internal logic (workings), you may find that there is a structure in this logic, which creates a vertical stacking of references. those are stages of development, and they consist of content, meaning experience, and the way this has been ordered. so a function is a line of developement, a building up of complexity, the education of which requires years and results in higher quality of the content. both judgement and perception create an inner world using differentiation. over time educated perception can perceive or imagine objects, that used to be invisible and impossible. these objects consist of other objects like three dimensions consist of two dimensions. this is what i call vertical reference or order. for most observers, the order of stages could more easily be seen in ethical or strategical reasoning (F or T), but vertical structure is just as essential in perception. therefore it seems insanely wasteful to abandon achieved vertical order of one line and start anew somewhere else, just to quickly adapt to a different external situation. it will result in lesser vertical quality. so instead we simply add new lines of intelligence, to the one's that we have educated so far, or differentiated as carl jung calls it. our subjective focus may to some degree move on to the new line, but the previous line won't go out of development, because it's development is never finished. study of lines of intelligence proofs that differentiation is always possible, like moving on through a fractal. the order in which we choose the lines (functions) that come next, as it is pointed out in common mbti circles, is just wrong. it's a different order. and it perfectly explains your subjective experience so far. it's all part of your type. it's natural development. the type is defined by it's history. it's point of starting out in differentiation. this is what makes a person unique. and the type.