Given that all science is done by humans, the TPS Paradigm defines as a phenomenon anything that humans can perceive or can make perceptible (e.g., technically) and/or that humans can conceive. (This notion that differs from various philosophical thought traditions, such as Kant's). 

At the metatheoretical framework's core, there are three abstract properties that can be conceived in different constellations for every phenomenon studied in research on individuals.

These particular properties are considered because they determine perceptibility of a given phenomenon by humans - and thus also by researchers. Given this, they also determine accessibility of many further properties that can be perceived in the study phenomena (e.g., colour) or inferred from them (e.g., causal mechanisms) and that are largely within the focus of research. 

Their labelling as metatheoretical indicates that these properties are conceived on a level of abstraction not commonly considered; but only time and space constitute ontological categories (Uher, 2013, 2015a, 2015d, 2018c).   

The three metatheoretical properties and the particular constellation of their forms are used to conceptually differentiate various kinds of phenomena studied in individuals. These are metatheoretical categories of phenomena defined on the basis of their modes of accessibility; they are not meant to constitute ontological categories (Uher, 2015a, 2015d, 2018a, 2018c).

These conceptual differentiations, as they are based on modes of accessibility, have important implications for research methodology as specified in the paradigm's methodological framework

What is behaviour? What is the psyche? Building on the metatheoretical differentiations, the TPS Paradigm also provides metatheoretical definitions of the phenomena studied.