Is Absence of Evidence, Evidence of Absence? Part 1

By Shaun

1. Introduction

The famous British philosopher Bertrand Russell was asked what he would say if he found himself before God on Judgment Day and God said to him, “Why didn’t you believe in Me?” Russell shot right back: “Not enough evidence, God! Not enough evidence!”

Many have taken what they consider to be an apparent lack of evidence for God as evidence that God doesn’t exist; that is, they look around, don’t see “enough” evidence and conclude that atheism is true.

But Russell realized that the inference from apparent lack of evidence for God to atheism is fallacious. That’s why in his famous debate in 1948 with Frederick Copleston he preferred the label “agnostic” instead of “atheist.” Yet today, many call themselves “atheists” when really they are agnostics.

Let’s first define some terms around the question “Does God exist?”

"Does God exist?"
Theism: "God exists"			Non-theism: "I don't believe in God"
	Agnosticism: “I don’t know if God exists”				Atheism: “God does not exist”
Hard Agnosticism: "I don't know if God exists and no one else can know either."				Soft Agnosticism: "I don't know if God exists, but it's possible for someone to know."

Notice a few things about these definitions. First, non-theism and agnosticism are not mutually exclusive because you could be a non-theist and so fail to believe in God (i.e., you could lack belief in God) but you might also be an agnostic saying, “For all I know, God exists. I just don’t know.” Notice also how extreme hard agnosticism is, since it claims even more than atheists do; the hard agnostic says that everyone is wrong, both atheists and theists, and that they cannot know what they claim, even if they have apparently sound arguments! Little wonder, then, that hard agnosticism is sometimes called “ostrich agnosticism!”

There are sound arguments for God’s existence. Some of them are very good. But suppose it were not so; suppose all the arguments for God fail and there are no further good reasons to believe in God. What follows?—Atheism? It’s very important to realize that the answer to this question is NO. What follows is, at most, soft agnosticism.

2. When Does Absence of Evidence = Evidence of Absence? (Or, when is the inference from “I see none” to “there is none” valid?)

What I have said so far raises the question, When does the absence of evidence become evidence of absence? This is a good question because sometimes (but not always) the former implies the latter. Let’s start with some examples to work with.

Example 1. Elephants in the Room (Absence of Evidence = Evidence of Absence)
Someone asks, “Are there any elephants in the room?” After looking about and seeing none, I say, “No, I see none. There are no elephants in the room.”

The inference from “I see none” to “There are none” in this example is justified. With respect to elephants in this room, I’m not agnostic; rather, I positively affirm: There are no elephants in the room. In this case, absence of elephants in the room is evidence of their absence. But this inference doesn’t hold for Example 2.

Example 2. The Grand Canyon Fly (Absence of Evidence ≠ Evidence of Absence)
We’re standing atop the Grand Canyon and someone asks, “Is there a fly way down there?” After a quick glance I say, “No, I see none. There is no fly down there.”

As in the last example we move from “I see none” to “There is none”—but unlike the last example the conclusion is unjustified. Agnosticism regarding the fly is the appropriate response here. So in the Elephant Example we don’t have to be agnostics, but in the Grand Canyon Fly Example we do. Why? Notice that it is not the relative size of the object which creates the difference (The zookeeper might have asked you on your zoo trip, “Do you think an elephant is in the cage in the next room?” to which your reply might be agnosticism: “I have no idea. Maybe.”)

The salient difference between these two examples has entirely to do with your epistemic situation — which is, roughly, the extent and limits of your ability to know something through your primary sources of knowing (i.e. perception, memory, introspection, testimony, etc.) — and the fact that only in one situation (Elephants in the Room) do we expect to have knowledge which we lack. My epistemic situation regarding knowing whether an elephant is in the room is quite good, while my epistemic situation regarding knowing whether a fly resides at the bottom of the Grand Canyon is quite poor. Why? When are we in an epistemically good situation in order to say, “There is no X”? What conditions have to be met? At least two. In the absence of evidence of an object O you may deny that O exists only if these Criteria are met:

Evidence Expectation Criterion. If an object O existed, then we would expect there to be evidence for it.

Knowledge Expectation Criterion. If there were evidence of object O, then we would expect to have knowledge of the evidence.

In short, in the absence of evidence, we can deny the existence of something O only if we should expect to possess evidence sufficient to know that O exists but in fact lack it.

To prove his position the atheist has his task cut out for himself: What he must do is show that (a) the epistemic situation in which we find ourselves with respect to belief in God’s existence satisfies the above Criteria; and (b) demonstrate that we lack sufficient evidence for knowing that God exists. Equivalently, he must show that all the arguments for God are unsound and then argue that if God existed then we would expect to be in a position to know whether God exists. But as we’ll see, there is good reason to think (a) is false because our epistemic situation in which we find ourselves with respect to belief in God’s existence does not satisfy the above Criteria.

Source: ReasonableFaith.org

Read Part 2