It is commonly accepted that the lack of evidence for a particular proposition makes belief in said proposition irrational.

However, imagine the following proposition,

P: An object exists for which evidence can never be comprehended nor even acquired by humanity.

This seems a certainly reasonable proposition, and in fact, belief in this proposition seems to be completely rational. After all, the universe is vast and perhaps infinite, and due to said vastness, the probability that such a thing exists which we can never reach, and, even if we did, would never be able to grasp due to our limited intelligence and perception, seems, to me at least, rather high.

And yet, by its design, this object has no evidence.

So, is this an example of a proposition which has no evidence but which it is still rational to believe in, and hence the premise that "each belief in something which has no evidence is irrational" ... is false?

One may counter-argue that the knowledge that our intelligence and perception is limited, coupled with the vastness of the universe, is itself evidence that such an object must exist. However, now I feel we are moving the goalposts and changing our definition of the word "evidence" into something less tangible and moving into the territory of probability, and it is well-known that probability is ridiculously hard to define and almost always subjective. If that is how we then wish to play the game, then "I believe in God because the probability that all of this came of nothing is so low according to my subjective probability distribution" must be considered an acceptable piece of evidence, which I don't feel it is.

  • Wittgenstein spoke of certain beliefs that are so fundamental that we never seek evidence for them. Such beliefs have a more solid foundation than what evidence could provide. He said, "Moore does not know what he asserts he knows, but it stands fast for him, as also for me; regarding it as absolutely solid is part of our method of doubt and enquiry." Wittgenstein thought it was unnatural to speak of knowing such thing because their certainty is not subject to evidence, so it's more natural to say "God exists" rather than "I know God exist," as if evidence were necessary.
    – user3017
    Oct 2 '17 at 18:55
  • The usual objection is that this proposition is not only unreasonable but plainly meaningless. Our understanding of concepts like "object" and "exists" is based on some sort of perception/interaction, at least indirect. So what can "object for which evidence can never be comprehended nor even acquired" possibly do other than string words together? Before one argues for or against such an "object" the hurdle to overcome is to explain how such a thing is not an empty phrase, what Kant called "transcendental illusion".
    – Conifold
    Oct 2 '17 at 19:40
  • Of course, when Kant was speaking of transcendental illusion, he wasn't speaking of the foundational truths that make knowledge possible. He asserted that we have certainty of certain non-empirical things, without which we couldn't grasp any empirical evidence: "[W]e might easily show that such principles are the indispensable basis of the possibility of experience itself, and consequently prove their existence a priori."
    – user3017
    Oct 2 '17 at 20:02
  • The conscience of man testifies, as a matter of certainty, to the existence of objective moral truth, and that, in turn, presupposes God's authority whose existence is naturally recognized by mankind in other ways as well. Man's failure to acknowledge such thing is due to sin and a refusal to become reconciled with God. Thus, the epistemological hurdle is overcome first by repentance and then by learning the details which God has revealed in His word.
    – user3017
    Oct 2 '17 at 20:40
  • @PédeLeão The a priori principles ("transcendental subject") are not exactly things, and they lack content without sensible intuitions. I think this is where Kant limits reason to make room for the faith, there is no knowledge of God we can have, a priori or empirically, nor is moral truth a matter of certainty, nor is its relation to God if it was. But we must act, and practical reason demands those things regulatively. But it does not seem to me that OP has something like God in mind, and one can certainly argue that evidence of God's existence can be both acquired and comprehended.
    – Conifold
    Oct 2 '17 at 23:41

Your question consists of two parts, 1) "What defines lack of evidence"?, and 2) "is it irrational to believe in something without evidence"?

In order to answer the first part, we must recognize that there are different amounts/types of "evidence" that result in different "degrees" of certainty. There is, 1 - no evidence, 2 - preponderance of the evidence, 3- beyond a reasonable doubt, and 4 - absolute certainty.

For some people, any degree other than 4, would constitute "lack of evidence" for others, only degree 1, would.

The answer to the second part then, depends on the mentality of the person providing the answer.
For a person that requires only degree 1, there are 3 additional degrees that "provide evidence," therefore it would not be irrational to believe in the item in question. whereas, for a person that requires degree 4, it would be irrational to believe in something supported by the lesser evidence provided by degrees 2 & 3.

  • I think the a component of irrationality comes when you believe something over a large number of equally likely alternatives without any particular evidence to support that. Believing in, say, a invisible pink unicorn in your garage is highly irrational partly because there's millions of other invisible pink animals it could equally likely be. Oct 12 '17 at 17:43

Awesome question! I was just commenting on evidence in a post focusing on conspiracy theory.

As others have suggested, different philosophers have different ideas about what constitutes "evidence," "truth," etc. I up voted Guill's answer because it emphasizes the fact that there are different amounts/types of evidence.

However, he listed some amounts, but not types, so I'd like to elaborate on the latter.

There's direct evidence, which may include "smoking gun evidence" (best of all, a signed confession).

There's circumstantial evidence -- evidence that tends to prove a fact by proving other events or circumstances which afford a basis for a reasonable inference of the occurrence of the fact at issue

In politics and conspiracy science, we may focus on historical patterns and connecting the dots.

For example, if you know that conquest, intimidation, conspiracy and exploitation were attributes of the Greek empire, the Roman empire, the Spanish empire and so forth, you might suspect that these are attributes of ALL empires, including the current U.S. government.

And if you know that Bill Gates' wife and pal (Warren Buffet) both sat on the Washington Post's board of directors, you might "connect the dots" (a form of inference) and suspect that Gates is using his power to influence the media.

Another type of inference is used in studying evolution. Having already established the fact that organisms evolve, scientists can assume that modern whales must have evolved from some other organism. And if they haven't yet found fossils of whales' direct ancestor, they commonly refer to it as a gap in the fossil record (or "missing link").

Yet another form of evidence is reality. If the media tell you the government's doing a great job, the economy's improving, blah, blah, blah, but your salary is stagnant, your benefits are doing downhill, and you see more homeless people on the streets every week, you might be a little suspicious.

Then there's "God." Some people say everything we see is evidence of his (or her) existence, while others say there is no evidence for God whatsoever.

In summary, instead of asking WHAT determines lack of evidence, we might ask WHO determines lack of evidence. There's a lot of cherry-picking involved. Consider judges' often mind boggling ability to dictate what's admissible as evidence and what isn't.

Your second question is more complex. What do you mean by "no evidence" - no DIRECT evidence, or no evidence altogether?

And what do you mean by "believe"? Are you talking about a rock solid belief, or do you include suspicions or theories?

With a background in science, I'm personally inclined to not believe in anything for which there is no evidence. However, that evidence can be indirect or even theoretical.

If I'm not mistaken, Carl Sagan believed in the existence of intelligent species on distant worlds, though there's still no real evidence of their existence. On the other hand, we might argue that Earth itself is evidence. If life can evolve on a planet in our solar system, why can't it evolve on planets throughout the universe?

What's really interesting is Sagan's rationale explaining his theory that "space aliens" have never visited Earth. How do you explain the actions of beings that may not even exist? Yet Sagan used some elegantly simple logic to form an explanation that further tells us that UFO's are not associated with space aliens.

P.S. Another thing I forgot to mention is familiarity with evidence. I recently read a story about Stephen Gould (of evolutionary science fame) visiting a dig in Kenya (Olduvai, I think). The Leakey family was renowned for their ability to spot the fossilized jaw of a mouse at a distance, something Gould couldn't do. Yet Gould, who did a lot of work with snails, was the first to spot a fossil snail at the site.

So when someone says "That isn't evidence," it's possible they can't recognize the evidence because they don't have the proper training or experience, or they could be a propagandist who denies the evidence that's in plain view.

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