Biologists frequently describe living systems using levels such as molecular, cellular, organismal, and ecological. These distinctions are often useful because scientific investigation requires complex systems to be divided into manageable domains of analysis. Different explanatory levels allow researchers to focus on particular aspects of biological organisation without attempting to explain the entire system at once.
APS accepts the practical value of such levels but rejects the inference that they correspond to distinct layers of biological reality. The levels used in scientific explanation are epistemic: they arise from the organisation of inquiry. They help structure investigation, communication, and theory construction. They do not necessarily reveal how living systems are organised in themselves.
This distinction is important because explanatory abstractions are often mistaken for ontological structures. The fact that biology employs molecular, physiological, developmental, ecological, or evolutionary explanations does not imply that living systems are divided into corresponding levels of existence. The organisation of life remains continuous even when scientific analysis partitions it into separate perspectives.
APS therefore distinguishes between levels as tools of explanation and claims about the structure of biological reality. Scientific inquiry may require levels; living systems do not.
Key Point. Epistemic levels are ways of organising biological explanation. They should not be mistaken for ontological levels within biological reality.