Empiricism has never been a uniform doctrine. Taken as a general attitude, there is something about empiricism that rings with a robust sense of reality that philosophers and scientists share as human beings who spend most of their waking hours outside of the classroom or laboratory. Most of us have probably come across the Thomas Paines of society who embody an almost self-assured realism that verges on the naive, the kind that professes a healthy dose of skepticism and common sense as antidotes against beliefs that lack “empirical” rigor: embodied, in short, by the kind of person who thinks he is qualified to make statements about science and religion but is an expert in neither. In addition, there are accomplished scientists who interpret reality according to the scope of a particular field of positivistic science and its theoretical models of phenomena (most of which are mathematical) without examining the philosophical presuppositions that go unnoticed in the process. Given these caricatures, and given the nuances involved, a thorough definition of empiricism is no simple task. [End Page 124]
In this article, we will instead attempt an overarching exposition of two overlapping but divergent paradigms of empiricism: (a) strict empiricism, representing most of the British empiricists and ancient skeptics and (b) mitigated, or metaphysical,1 empiricism represented by Aristotle and St. Thomas Aquinas. Sense experience is the unifying departure point for both, but while (b) says that human knowledge begins with sense experience, (a) tends to ultimately reduce knowledge to sense experience. Concerning structure, our article is divided into two parts. The first consists of two sections: (1) a philosophical critique of strict empiricism from the viewpoint of mitigated empiricism and (2) an account of how both versions of empiricism view causality. The second part consists of a critique of strict empiricism from the point of view of mathematics and modern physics. Since the very scope of these topics has generated a vast literature, the sole aim of our thesis can be only to raise questions about certain empiricist presuppositions that enjoy wide appeal, especially in the English-speaking world. Beyond the philosophical benefits of critiquing the strengths and weaknesses of an influential tradition such as British empiricism against a philosophical tradition that is often neglected or misunderstood, some of the advances in mathematics and the physical sciences over the last 250 years suggest that the complexity involved in the study of the natural world raises serious questions about any version of strict empiricism, specifically, the development of nonlinear dynamical systems, special and general relativity, and quantum mechanics, all of which challenge the presuppositions of a strict empiricism.
II. Strict Empiricism and Metaphysical Empiricism
A. A Critique of Strict Empiricism
It may seem irrelevant at this juncture to mention the name Parmenides, but in reality this ancient Greek philosopher represents the state of the question. To Parmenides, the universe offers a convincing impression of motion, multiplicity, and change, all of which are registered [End Page 125] by our senses. But human reason “sees” something the senses do not: that what all things have in common is that they exist. For Parmenides, existence does not come in degrees because:
1. The already existent cannot be the source of more existence (existing is existing, period);
2. The existent cannot emerge from that which does not exist (to say that existing and not existing is the same thing is a contradiction that reality does not permit).
If the difference between thing x and thing y is nothing (since they both exist), sense experience and change must be at best an illusion. Unable to arrive at the concept of the potentially existent (not to be confused with possibility, which is a logical category), Parmenides affirms the principle of noncontradiction at the price of severing any causal connections between a conclusion of reason and the input of the senses. Parmenides comes close to making an explicit discovery of a distinction that would elude the British empiricists: the distinction between sense knowledge and intellectual knowledge.
Leaping across centuries, we find that Descartes himself is unable to escape relative nonexistence. I...