Knowledge empiricism, as propounded by men like Locke, Hume, and Berkeley, is the doctrine that all a priori knowledge is of analytic propositions, while synthetic propositions can only be known a posteriori. Concept empiricism is the doctrine that all concepts are derived from experience: there are no innate concepts. Knowledge rationalism is the doctrine that there is a group of synthetic propositions that are known a priori, while concept rationalism is the doctrine that there are innate concepts.

The academic community of philosophers has long since moved on from the debates between the empiricists and rationalists – largely thanks to Kant – but empiricism has left a legacy in the form of the popular understanding of science. Much of the misunderstanding in the science versus religion debate stems from this source, notwithstanding the fact that many of the empiricists were theists (in my opinion the jury is still out on Hume).

Hume’s ‘fork’ expresses the analytic/synthetic distinction as “relations of ideas” (analytic) and “matters of fact” (synthetic). We can have certainty regarding “relations of ideas” through the process of deduction – but we cannot know that these ideas express any truth about how the world is. “Matters of fact”, despite the name, cannot be known with certainty: they rest on causal inference. Our experience is subjective, which is why Hume’s ‘fork’, taken to its logical conclusion, leads to Berkeley’s idealism, the rejection of physical objects as expressions of the ‘material substratum’.

Regarding religion, the consequence of accepting Hume’s ‘fork’ is that proof of God’s existence becomes impossible. If the proposition “God exists” is analytic (“relations of ideas”), then it says nothing about how the world is, which makes it irrelevant to living religion in the lives of humans. If the proposition is synthetic (“matters of fact”), then it is impossible to attain certainty regarding its truth. It becomes a matter of faith – for which we may nevertheless make cogent inductive arguments. But note: Hume himself was sceptical regarding these arguments. Paley’s argument from design was ultimately rejected by Hume: he could acknowledge the possibility of a Designer, but he argued that Paley had failed to prove that the Designer was God, much less the God of orthodox Christianity.

So, who possesses more faith: the empiricist or the rationalist? The empiricist does. His scepticism requires faith to affirm the following hypotheses:

  • the external world exists;
  • the external world is (more or less) how we think it is;
  • other minds exist;
  • God exists.

Note that Bishop George Berkeley, while a radical empiricist, made his own argument for the existence of God.

  1. My perceptions are caused by:
    1. ideas;
    2. my mind;
    3. another mind.
  2. Ideas are passive; they cannot cause anything.
  3. If my perceptions were caused by my mind, then I would be able to control them.
  4. I cannot control my perceptions.
  5. Therefore, my perceptions are caused by another mind that compels me to experience perception.
  6. Given the power of that mind and the complexity, regularity, and systematicity of my perceptions, that mind must be God.