To start, I am a proponent of empiricism but feel like I stumbled into a flaw.

How come we only accept what we can repeat? ..and how often do I need to be able to repeat to the same conclusion for me to accept it?

For instance, if I experienced a ghost once, why don't I accept that there are ghosts, even if I never see one again? And also, If I lived infinite days, and every day the sun rose, how could I reach a definitive conclusion that the sun will rise again?

So, to me it seems that this makes empiricism flawed, in that my senses could never conclude repetition/pattern.

Where am I wrong? or am I right? ..also, is the repetition/pattern similair to what Kant talked about when he said we have a priori unity of experiences?

  • 'of of' - typo corrected: GLT
    – Geoffrey Thomas
    Dec 27, 2019 at 10:22
  • 4
    Since when "we only accept what we can repeat"? All historical events are non-repeatable, but we still accept most of what is written in reputable history books based on credible sources.The problem with ghosts is not that encounters with them are not repeatable, but that credible evidence of them is lacking. And the Sun will run its course, like any other star, in finite time, so there will be a day when it no longer rises. The flaw you speak of does not exist, empirical disciplines studying non-repeatable events simply have different methodology.
    – Conifold
    Dec 27, 2019 at 10:32

3 Answers 3


From an epistemic approach, and from the perspective of empiricism, causality (for instance) is a type of knowledge acquired through custom and habit. So, you are asking how many times an event should repeat for it to be considered customary and habitual. That is dependent on multiple factors, not only the subject but also the object and the conditions of possibility.

From an ontological approach, there's no absolute truth. If you see a ghost once, and you are sure of that, it is enough for you to consider the existence of ghosts is a subjective truth. If you cannot repeat the experience in front of others, the shared truth (for some, shared subjectivity, for others, objectivity) is that ghosts do not exist. But there's no final truth. Science does not express scientific truths, but empirical truth. The type of knowledge that empiricism refer to is mostly subjective knowledge, which features quite arbitrary modes of truth.


To enlarge upon Ted Wrigley's answer: In scientific investigations, there is always a chance that what you think is a signal is instead a random fluctuation. Fortunately, the mathematical tool of statistics furnishes rigorous rules for distinguishing between random flukes and real signals, knowing the repeatability of the signal detector. Those rules furnish the experimenter with means of quantifying the probability that a given signal is real and the most common way of doing so is by repeating the experiment a number of times and comparing the results with what one would expect on the basis of random chance. This is why scientists and engineers are obsessive about repeatablity both of their measurement tools and of the phenomenon under study- and why they must repeat their experiments many times.


enter image description here (courtesy xkcd)

Common misperception: replication isn't about the mere act of repeating things. The point of replication is to make a convincing case that a systematic rule exists, such that we can be confident that a given set of actions will produce a given set of results. How many times do you need to stick your finger in a power outlet to convince yourself that it's a reliable source of electric shocks? Twice? Maybe three times? More is just masochism...

When you experience something, you've experienced it; there is no question about that. The problem lies in two questions:

  • Was what you experienced a one-off fluke or aberration, or something you should treat as a real phenomenon?
  • Can you convince other people that you actually experienced it, or are you going to sound like a loon talking about it?

In order to answer either question, you need to be able to repeat the experience so that you or others can see it again. If you've seen a ghost, you've seen a ghost. You might be imagining things, or outright hallucinating, but you've still had the experience. Can you set up the conditions to produce the ghost again, so that you can see it, and others can see it? If you can, then you've shown that the experience is replicable, and that by itself is enough to add credibility to your claim.

In the academic world people can get obsessive about replication. They will test something dozens of times, in different variations and conditions, in the hopes that they can 'break' a theory. That's good and useful in that environment, because breaking a theory in academia is an important part of constructing new and better theories. But in the real, practical world we don't need to repeat something over and over and over to convince ourselves that a rule is in play. Common sense dictates otherwise.

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