This blogpost is dedicated to Justin, a 12-year old intelligent friend of mine.

Justin has asked a very important question: How do we know that God exists as an extra-mental reality instead of merely as an idea or imagination inside our minds?

Since I noticed there is a small tank of fish (plural) in Justin’s home, in this blogpost I shall use one of Justin’s fish to prove or demonstrate the extra-mental existence of God (there will be a second blogpost to complete the proof but the most important part is in this blogpost).

Here is a sketch of my Stage-1 proof to Justin that God exists as an extra-mental reality, base on the fact that a fish exists in Justin’s fish tank:

1. The traditional idea of God (ie Classical Theism’s idea of God) is: God is someone whose existence is absolutely unconditional on any condition. In other words, God’s existence is unconditional existence. In contrast, a living fish’s existence is continuously conditional on many conditions such as the existence of blood in its body, the existence of water around its body, and many other conditions. So is there any entity that exists unconditionally in the real world outside our minds, rather than merely as an idea in our minds?

2. Let us consider a fish swimming now in Justin’s fish tank. Among many different real world conditions which that living fish depends on for existence, there is this particular series of concurrent conditions which that fish (swimming now in Justin’s fish tank) is continuously conditional upon in order to exist:

        fish < blood < plasma < …

(a) If all the blood is removed from that fish, what is left would be a dead fish. A dead fish is not a living fish. Hence if all the blood is removed, that living fish would no longer exist. Therefore that living fish’s existence is continuously conditional on the concurrent existence of blood in its body. 

(b) The blood’s existence is in turn continuously conditional on the concurrent existence of plasma. This is because: if all the plasma is removed, then what is left would no longer be blood but some dry residue. 

(c) The plasma’s existence is also continuously conditional on some further concurrent conditions (eg water which is a major essential component of plasma).

3. Since that living fish is empirically existing now in Justin’s fish tank, this means that all the concurrent conditions in the above-mentioned series have been fulfilled. If any one of those concurrent conditions failed to be fulfilled, then the living fish would not be existing as a living fish now. If any one of those concurrent conditions fails to continue to be fulfilled in the next hour, then the living fish would cease to exist as a living fish in the next hour.

4. The above-mentioned series is either an endless series or a series with an ending.

5. If that series is an endless series, then fulfilling all the series’ conditions would be an endless task, just as attempting to count all the positive integers [1, 2, 3, …] is an endless task. In other words, if that series is an endless series, then it is impossible for all the conditions in that series to be fulfilled. In such a situation, that living fish would not exist in Justin’s fish tank. But the empirical fact is: that living fish is existing now in Justin’s fish tank. Hence that series is not an endless series; that series has an ending. In other words, that series of conditions has a very last condition as follows:

fish < condition 1 (eg blood) < condition 2 (eg plasma) < … < last condition 

6. Since the last condition (of the series of concurrent conditions) exists, this means the last condition exists without being conditional on any further condition. (Otherwise the further condition would instead be the true last condition of the series.) This last condition is existing unconditionally in the real world outside our minds.

7. Preliminary Conclusion

The empirical fact that a living fish exists now in Justin’s fish tank entails that in the real world outside our minds, there is something or someone existing unconditionally.

I shall use another blogpost to demonstrate why:

(A) In the whole of reality, there is only one entity that exists unconditionally while every other entity exists conditionally.

(B) Why this one and only one unconditionally existing entity is not something impersonal but someone personal (ie someone with a mind).

(C) Why this unconditionally existing entity is what Classical Theism calls God.