This study seeks to explicate the philosophical foundations and theoretical outlines of grey systems theory by focusing on human perception, cognition, and understanding processes and by considering their functions in the process of producing knowledge. Primarily, the study investigates the processes of perception, cognition, and understanding, as well as their dynamicity. Then, it is explained how knowledge is produced through the interpretation/understanding of information and data and through the dynamicity governing this process. The findings reveal that human perception, cognition, and (...) understanding perpetually remain grey and imperfect, while lost sensatory data mark the very first aspect of greyness in such human capabilities. Furthermore, any piece of data, as a discrete and single entity, represents a determinate fact, symbol or signal from the world, while any set of data, no matter how large, remains incomplete and imperfect, and human beings always interpret inadequate sets of data in the world. Therefore, information and knowledge always remain grey and uncertain because they deeply rely on subjective understandings/interpretations and work with imperfect inputs and sets of data. The impact of knowledge on action and interaction and their effects on the world are some factors adding to the dynamicity of the world. Constant change in world data, outdated knowledge, defects in datasets, and human biases in understanding all confirm the infinitely grey nature of human knowledge of the world. (shrink)