One of the most fundamental questions in epistemology and arguably in philosophy is the question of certain knowledge. It is a cornerstone of epistemology and, along with the various definitions of truth, stands among the most debated questions in the field. In this essay, it is my goal both to describe the current state of discussion regarding the question of certain knowledge and to express my views, discuss arguments against those views, and respond to said arguments.

In epistemology, there are differing views of truth and what can, or ought to be, seen as a source of truth. Perhaps the two most prominent of these views are empiricism and scepticism. Empiricism is backed by the idea that senses should be seen as a source of truth, but further, complex interpretation of those senses should not. For example, David Hume, a Scottish empiricist, would argue that he may claim that a cue ball in a game of billiard moved, and hit another ball, which then also began to move, but he would also refuse to claim that he knows for certain it is the collision between the two that caused the motion of the latter. In this example, Hume only acknowledges his senses and experiences, but makes no claim as to the certainty of deductions based on those experiences. Sceptics, however, do not see human sensation as a reliable source of truth. They argue that very few things, or even nothing, can be known for certain, and as such every thought and belief should be subjected to merciless scrutiny, relying exclusively on what is absolutely certain.

These are only two of the many points of view from which the problem of truth can be approached. Additionally, on a personal basis, these ideas are often combined to form new and intriguing ideas of what ought to be seen as true, or what ought to be considered to be absolutely certain. I find that both empiricism and scepticism are lacking in some aspects, which I believe are fundamentally important to understanding both the questions of source-of-truth and certain knowledge as well as any reasonable answer to them.

At the level of the individual, empiricism is largely inapplicable outside of everyday life, because it is only useful as long as one assumes their senses to be an accurate representation of reality. This is simply false in the event of an optical illusion or an auditory hallucination, and even if we disregard those cases as too uncommon to be relevant, it still raises questions about the existence of a true, objective reality in the first place. As such, scepticism stands out to me as the more logical and reasonable of the two ideas. Despite this, it remains important for me to clarify both that scepticism is not without flaw and that scepticism is, as opposed to empiricism, applicable in and of itself only outside of everyday life. This is why these ideas must be combined elegantly in order to produce a world view which is based on agreed-upon logical premises but also holds true both in abstract discussion and in everyday life.

To answer the source-of-truth question and, by extension, the question of certain knowledge, we must first consider experience. Experience can be divided into two distinct categories, which allow us to more define source-of-truth in a way that is simultaneously logical and applicable in everyday life. These categories are introspective experience, that is to say, experience of self, and extrospective experience, experience of external reality.

I argue we can have certain knowledge only in the case of introspective experience — one can know that they have experiences, and by extension that there is an experiencing agent, them, which is having the experiences, and additionally, that there must be a source of experience. Importantly, the framework of reason within which we operate is largely inapplicable in the context of this experiencing agent — we cannot reason as to the nature of the experiencing agent, as we have no premises from which to reason. One can know for certain only what logically follows from the fact that they experience.

The larger area of extrospective experience concerns not the experiencing agent themselves but the object of experience, interpretation of experience, and deduction based on experience. This, then, is the area of uncertainty — there can never be certain knowledge of this area, as the experiencing agent’s interpretation of the extrospective experience need not match the source of those experiences. This is not to say that it is necessary or useful to question the subjective interpretation of extrospective experience, as a sceptic might. Rather, it is useful for everyday life to assume that this interpretation corresponds to some fundamental fact about the source of experience, even if the truthfulness of this assumption is not certain. This way, we may abstract away all uncertainty that is not useful in the context of everyday life. When we claim that the collision of a moving cue ball and a stationary billiard ball is what causes the latter to begin motion, we do not claim that we have absolute certainty of this fact, rather we claim that any uncertainty is negligible, and we would simply be surprised if our claim was to be incorrect.

In conclusion, over the past two millennia, various stances have been taken in order to propose answers to the question of whether certain knowledge exists, or more generally, what things should be regarded as sources of certain knowledge. As a potential solution, I propose two main categories of knowledge — one, knowledge of introspective experience, is certain, whereas the other, interpretation of extrospective experience, is not. This also implies that I cannot be certain of the validity of this proposition — yet by way of shared premise and logical deduction I can attempt to convince others of it. The question, then, grows in complexity, as there is no longer a single, definite answer: yes, certain knowledge does exist, but only in the scope of introspective experience. Certain knowledge of the external world, I argue, does not exist.