The development of and standardization of metrics was critical to the development of science. The standard metrics provided "objective" standards for describing events and experiments to ensure that they could be replicated and generalized appropriately. Without objective standards of measurement there could be no science.
Development of objective, observer independent standards of measurement was essential to the success of the physical sciences.
However, the great error in Western Science was to take the description of the world in terms of these metrics as an objective reality - in opposition to a subjective reality! The implication is that the objective distance in terms of meters is true, but the functional relations such as graspable, reachable, near or far are 'subjective.' This implies that the variability associated with individual differences along such dimensions is "noise" with regard to the "true" reality. And there is an implication that this "noise" has to be somehow filtered and added-to in order to construct a mental model of the objective truth - in relation to the standard metrics (e.g., the size in meters).
One implication is that since people and animals are not well calibrated to the standard metrics, then their perceptions of the world must be 'indirect' and therefore it is necessary for them to reconstruct the true world (recover the correct standard) in order to act appropriately.
Another implication is that many of the relations that directly impact how people make judgements about graspability (e.g., their own hand size), reachability (their arm length or height), or closeness (e.g., available modes of transportation) are less real - less basic - or that they are derivative. But of course, these relations are every bit as 'real' and every bit as specifiable as the elements comprising these relations.
These relations are part of a "whole" that can not be discovered in the components. These relations are 'emergent properties' of the whole. A central premise of ecological psychology is that these emergent properties are 'essential and fundamental' elements for a science that hopes to describe how people adapt to their ecologies. Ecological Psychology argues that the size of an object relative to a hand or the distance to a cliff relative to your height is every bit as objective as the size relative to a meter stick.
Further, ecological psychology argues that these functional relations exist in the world to be discovered and perceived directly. And that there is information (e.g., structure in optical arrays) that specifies these emergent properties. Thus, there is no need for internal processing to construct or reconstruct these relations. These are NOT mental constructions - they are functional properties of the coupling of an animal with its ecology - they are properties of the umwelt. They are affordances that can be directly experienced.
The mistake that Western Science has made is that it has taken the arbitrary metrics created to aid formal scientific enterprises as 'fundamental' and it has taken the relations that emerge from the functional interactions of people with their ecology to be 'derivative.' However, I think there is little doubt that the experiences of graspable, reachable, near or far are fundamental primitives of the human-ecology system. These pragmatic/functional relations are the raw primitives of experience. They are REAL! The metrics of objective science are also real - but they are the wrong level of description for exploring how people adapt to the functional demands of everyday living.
As Protagoras claimed: Man is the measure of all things.
In our everyday lives we directly experience the ecology in terms of the REAL properties that emerge as a function of the perception-action coupling with our ecology! We will never construct a satisfying understanding of human performance if we start by denying the reality of these essential emergent properties. Thus, the claim is that a science of human performance must be built using different bricks than those used to construct an 'objective' physical science. These bricks, these essential elements are different from those used by physicists, but they are no less real.
The essential elements for building a science of human experience are different than those that have been used successfully in building a science of an observer independent physical world. However, these elements are no less real.
The irony of using different bricks or working at different levels of description is that this may be the path that might allow us to escape from a collection of little sciences to a single, unified science, that spans the field of possibilities reflecting the joint constraints of mind and matter.
See What Matters for an exploration of the implications of these ideas for cognitive science and experience design.