We propose a definition of physical objects that aims to clarify some in-terpretational problems in quantum mechanics. We claim that the transformations induced by an objective property of a physical system must leave invariant all the other objective properties of the same system. The uncertainty principle is understood as a natural consequence of the imbrication between objective properties and non-objective properties. It follows from the proposed definition that in classical mechanics non-objective properties are wrongly considered objective. We conclude that, unlike classical mechanics, quantum mechanics provides a complete objective description of physical systems.