There's a certain evidence atheist on CARM who thinks that since there is no actual empirical evidence for God, God is only an idea in the mind and has no reality. There's another atheist who argues that absence of evidence can be positive proof of something, although he denies that it has to be proof of no God. Even though he denies this the two ideas re made for each other, one is the completion of the other. Despite the denial when atheists read the one idea (lack of evidence) we all know they are thinking of the other "God must not be real because he' s not localized and triangulable."
First let's deal with the lack of evidence issue. Here is Darth Pringle's post:
I can't believe that some theists (more recently, ferengi and Mr. Metaphysics) still appeal to the fallacious, "Absence of evidence is not evidence of absence". It is at least as fallacious as, "You cannot prove a negative". In the same way that some negatives can be proved (at least, beyond reasonable doubt) there are obviously situations when absences constitute evidence. Here are some examples ....Absense of evidence for God can never disprove God, it is impossible to prove a negative. These are not fallacie, the fallacy is in creating "atheist logic" that incorporates their logical mistakes into a canon of permissible moves. One thing he's doing that makes it seem permissible is his misunderstanding of "negative." "Can't prove a negative" doesn't mean you can't use a lack of evidence to assertin the unproved nature of an unsupported propostion. Here he's confusing the distinction the faliure of rational warrant due to lack of evidence with postiive proof of an absence. "Negative" means you can't disprove something just by pointing out no evidence. The thing disproved is the assertion of backing for confidence in the hypothesis "X exists." It is not actual proof that "there is no X such that X is (whatever is in question)."
Now he gives three examples of lacking of proof that supposedly prove something positive:
1. An absence of hair on a persons head is evidence that they are bald.First collapse the examples becuase they are multiplied examples of the same thing. They are all examples of something a case where one views that X is not there present, thus the absence of X proves the hypothesis "there no X such that X is (whatever is in question)." Secondly, this sort of question is fundamentally different from the question of God's existence, the existence of Jesus as a man in history. Lack of evdience as proof also comes into the atheist case for Jesus mythers where their major arguments are all arguments from silence sot hey try to infer from the silence a proof that no historicity of Jesus. This is fundamentally different from the idea that "if we have no direct empirical observations of God then this proves no God." The reason is not only becuase the situations are not analogous but because the kind of questions being asked are different.
2. The verifiable absence of a person at a crime scene (eg, on CCTV) when the crime was taking place is evidence that they could not have committed the crime.
3. The absence of a donkey in my lounge is compelling evidence that there isn't one there.
The idea that absences are never evidence is thus just as flawed as the idea that no negatives can be proved.
The sitautions are different because with the guy's head there is a limited space one can view directly to say "there is no hair, therefore, baldness ensues." There is no place to look in the univers to say "I don't see God here, therefore, there can't be God anywhere." Secondly it's a fundamentally different kind of question becuase hair is on object of sense data; hair is immediately within the purview of direct empirical observation. God is the basis of reality. This is what my slogan means when I say "God is not a thing, alongside other things in creation." It's a fundamentally different kind of question in dealing with the foundations of reality, because we have no idea what they are. Are they supposed to be empirically derived? We don't know. Presumably one would have to get outside of reality to look back at reality and determine if it's apprehendable, thus we can't say. Thus it cannot be argued that lack of empirical evidence for God is proof that there is no God.
It must be pointed out that absences cannot be used to defend some claims. Fir example, an absence of x at y would prove that there is no x at y but it wouldn't prove that there are no xs (unless x is omnipresent, then it would).That's an important admissible becasue it opens the door to the argument I just made.
However, if theists expect atheists to drop the questionable, "you can't prove a negative" then theists should be dropping the equally questionable, "absence of evidence is not evidence of absence" because neither is universally true in all situations and thus, the applicability of such claims must be tested against the nature if the claim being made.In a technical sense the hair thing is not an absence of evidence but an absence of hair. The evidence is the view of the head, which is not absent. It's all matter of what you construe as proof. or how you frame the question. The kinds of negatives being dealt with are fundamentally different. With the hair thing one is saying "the lack of something that should be empirically observable indicates the lack of that thing." With the God question one is saying the lack of empirical evidence of something not given in sense data (and therefore, not empirically given) is proof of the nonexistence of that or anything like it in all of reality. That's a much different sort of question. You can't prove a negative doesn't mean an absence never proves an absentee it means you can't prove the non-existence of something. You can prove the nonexistence of hair on a particular man's head but that's not really what the statement is getting at. You can't show the non-existence of a given thing in action." Here it is, here is the thing itself caught not existing. That's what's being said in the phrase "prove a negative."
In thinking about the corollary, that lack of imperial evidence means God is just an idea in the mind, there are realities that are not tangible. The intangibility of a given reality is not proof that it's only an idea in the mind. Examples: time is a reality. Time is not tangible. We can't go to a particular place and take a picture of time. We can't touch it, but it touches us always. Another example might be the laws of physics. No one really knows what they are. Atheists try to dismiss them as "merely a description of what happens in the universe" but that seems to be conflated. For example there are descriptions of possible for a universe that hasn't come to be yet. So how did the universe come to be? It could evolved out of some sort of on going process but then why does that process continue along certain lines with such great regularity? We have no proof that there are laws of nature, yet it makes no sense otherwise. To say they are merely descriptive (which not all science say and they didn't used to say) is merely to cut off the question about regularity.
Justice also seems to be a reality that is not tangible. One can say justice is surely just an idea in the mind. It even has different versions for different cultures. For some justice is equality, for others justice is punishment of the guilty, then of course that works itself into equal and fair punishment. None of that is proof that justice is not a real thing. When we don't have it the consequences of nothing having it are real.
God is surely more a reality that justice, which is probably an outgrowth of God's character or something along those lines. Yet, the reality of the concept surely indicates that there are realities beyond the concrete. Then one must face the question begging nature of the hypothesis. In other words, to assert that God is only a thing in the mind because he's not given in sense data is just begging the question with the assertion that only concrete tangibilities are real.
There is a large body of philosophical writing about the issue of abstractions being realities. Unfortuatnely I am not well versed in that body of work so I avoid being it up.