MonoRealism Philosophy Site

Doubt and Certainty

Philosophical Reflections VII

The world is objectively real, so we can learn about it by using reason to integrate sensory input, memory and experiment. I have examined and refuted a number of attacks on the inherent validity of reason and science. In addition, in passing I have touched upon certain fundamental questions about the limits of human knowledge. We now return for a more detailed analysis of these.


The two Absolutes form the bedrock of our beliefs. Each of us knows beyond any possibility of doubt that our consciousness exists, and that some kind of reality external to our consciousness exists. All the rest of our knowledge consists of our understanding of the nature of these two existents. As the reality we perceive is hard, it is possible to test our ideas against it, and thus to learn.

However, it is impossible for such derived knowledge to be absolutely sure: some element of doubt always remains. For example, the world we know might dissolve tomorrow, and be revealed as a complex illusion (and so on, ad infinitum).

This most fundamental of doubts is not based on any evidence, however: it is simply an inescapable logical consequence of the fact that external reality is external. The very reasons by which we know there is an external reality – we didn't create it, don't control it, and know it only by means of how it impinges on us – mean our understanding of its nature can never be an Absolute.

The same goes for all the tools of our consciousness, both fundamental (reason, senses, memory and physical action) and incidental (intuition and feelings): all are beyond absolute validation. For example, reason is the primary tool of our conscious mind, but is not designed by it (although by the use of reason we can work out explicit rules of valid & invalid reasoning). It is a "given" of consciousness, its basis rooted in external reality: therefore its reliability cannot be an Absolute. However, note that everyone must use the fundamental tools and thus assume their basic validity, even in the act of disputing them!

Doubt such as this, inherently beyond disproof but with no basis in evidence, I call "empty doubt".

Empty Doubt and Real Doubt

Empty doubt is essentially meaningless. By definition, there is no evidence for it. By its nature, we can't do a thing about it. Yet it is brandished by those who would destroy the human mind as if it were some sort of invincible weapon. "How can you know that our view of reality is true?", they ask. I ask: "How can you know that our view of reality is not true?" In the realm of logical certainty and logical doubt, these two questions are equal.

Yet, we do know that some sort of reality exists; we do know that it can get exceedingly unpleasant, if not fatal: it is, therefore, impossible for us simply to wallow mindlessly in the limbo of two equal and opposite empty doubts. By their nature, empty doubts are undecidable: therefore they are not tools of cognition, and have no value to a conscious mind in its necessary (Prime Principle) pursuit of knowledge. We must attempt to decide between propositions. We are thus forced into the realm of "real doubt".

"Real doubt" is doubt based on actual evidence. Since empty doubt is in principle undecidable, the only response open to a rational mind is to base its decisions and actions on its evaluation of real doubt: its evaluation of evidence. By this measure, there is no doubt that the external world is objectively real, and crushing doubt that it is illusory. By this means, we can learn about the world.

The hypocrisy of those who trumpet empty doubt has been noted before. Now we see why they are necessarily hypocritical: as conscious life, in reality they can survive only by operating in the realm of real doubt, whatever else they wish were true.

Empty Claims

An empty or "arbitrary" claim is a positive claim made without any appeal to evidence. The converse of empty doubt, it has the same logical status.

Clearly, empty claims are as meaningless as empty doubts. An equally "possible" contradictory claim or doubt can be made, forcing us into the realm of evidence. A simple example illustrates this. Someone may say: "I believe in God. I can't prove it, but you can't disprove it either! So your atheism is no more valid than my faith." Such a claim is easily deflated by a simple claim contrary to its central tenet: "I agree, God exists. But actually, He hates irrationality and will send all believers to hell, saving only those who live by reason. Prove me wrong!" This issue, like all others, must be decided on the basis of evidence.

A new hypothesis also may be unsupported, but there is a vital difference between it and an empty claim. The former seeks to explain something and predicts testable consequences; the proposer accepts the onus of proof. The latter might seek to "explain" something, but is not proposed in order to be tested and thus expand knowledge, but purely to cling to an irrational (unprovable) belief in the face of contrary evidence. Even a valid hypothesis, however, can also be an empty claim if it is misused, e.g., proclaimed to be true or used as the basis for ethical or other prescriptions.

The Onus of Proof

As empty claims are cognitively meaningless, the only subjects open to discussion are those where there is real evidence. In that case, the task facing any rational mind is to determine the best explanation of the evidence. There is no other basis for a decision. Therefore, the question of the onus of proof does not arise: the onus of proof is always on the evidence. But if the evidence is inconclusive, which explanation should you decide on (assuming you must make a decision)?

The only way we can learn about reality is by the way it impinges on us. Something that does not exist cannot affect us, so an absence of evidence is already a prima facie case for denial. Therefore, the onus of proof lies on the side which proposes the existence of something, not on the side which denies it. To earn the right to be taken seriously, the proposer must indicate how the thing will impinge on us: thus allowing the idea to be tested, bringing it into the realm of evidence. This is also why the simplest hypothesis is to be preferred, other evidence being equal ("Occam's Razor").

The Best Explanation

A valid theory of knowledge must be based on reality. External reality is hard: it impinges on us consistently in ways determined by its nature, therefore by using reason we can discover that nature. Human reality is that we are conscious, rational beings who have no instinctive knowledge of facts. By our nature, we can learn only extrinsically: from our senses, from the way reality impinges on us.

Therefore the only way a human being can gain knowledge about reality, and have any confidence in it, is by using his or her reason to determine the best explanation of all the facts available. As reality cannot be self-contradictory (A is A), true knowledge can't be either: thus a rational mind must strive for an integration of all its knowledge without internal contradictions. But can reaching the best explanation allow us to reach the truth?

The Truth

Our knowledge of reality has two overlapping parts: our knowledge of facts and our understanding of why they are so. The former is the observed nature of things that exist. The latter consists of theories and statements of natural laws.

Our knowledge of the facts of reality may be incomplete, but what we know, we know (to "know" requires due diligence in research and adherence to the laws of logic and evidence.) There may be further details to discover, but as reality itself is hard and cannot be self-contradictory, further probing of reality cannot invalidate earlier knowledge. Thus if we discover an inconsistency, we know we have come across some previously unknown factor.

We cannot know every single fact of reality: only something the size of the universe can hold all the information in the universe! Our power to understand the universe consists of our ability firstly to abstract the concretes of reality into concepts, and secondly to use logic to arrive at testable theories about it. The first allows us to think about innumerable concretes as a single unit, and the second allows us to discover the laws and principles which explain the facts of reality. The latter enables extreme compression of information: to describe the exact atomic structure of a single grain of sand would require a vast library; to describe the laws which govern the structure of all grains of sand requires a pamphlet.

Our understanding of natural laws is more prone to error than the simple collection of facts and their abstraction into concepts: as our theories explain rather than describe, they can't be verified as directly by reference to primary perceptions. However, the accumulation of successful precise predictions, and the building of further successful theories and technologies on their foundations, eventually proves them: in that no real doubt remains. Then one might still have grounds to seek to improve them, or find limits to them: but not to doubt their basic truth.

The ABO blood groups are a good illustration. Their existence and the resulting rules of blood mixing were established. Inconsistencies (clotting between supposedly compatible groups) showed up further blood factors such as Rh, thus extending the earlier knowledge without invalidating it. Further research then explained the blood groups by reference to surface molecules and the workings of the immune system. Much still remains to be learnt about the immune system, but the wealth of consistent data and successful applications proves the basic theory beyond all real doubt.

More Truth

Knowledge builds on knowledge. Almost a truism, this is the cause of the exponential growth in scientific knowledge. New theories suggest new avenues for investigation. The arduous life's work of one person becomes the starting point for another. New knowledge leads to new technology, which itself increases the rate at which further new knowledge can be gained, and so on in an ever-increasing spiral.

The result is the virtual disappearance of many former scourges of mankind; a massive increase in human productivity; everyday technologies and luxuries beyond the imagination of previous generations; the ability to fly around the world and to reach the planets. There can be no real doubt that knowledge builds on knowledge. But for this process to work, the knowledge being built upon must be fundamentally valid. The process works, with spectacular success. Therefore the knowledge is valid. It is true.

There are many pathetic things about modern philosophy, but one of the most pathetic is the moaning that we can't be sure of anything. We can be sure of what we know, with only empty doubt remaining: and empty doubt is cognitively meaningless. When a theory precisely accounts for a wide range of things and contradicts nothing known, then either it is basically true or it is an amazing coincidence. By definition, the latter is very unlikely. When we can make computers on a chip; when we can genetically engineer microbes as we like; when we can make tons of metal fly us through the sky at our command: we don't think, "Wow, what a bit of luck!" We know: "Such is the power of our minds to know reality and by knowing it, to turn it to our use."