The idea of existence has always been puzzling. Today I was wondering do people who are claimed to be existence actually exist? This is an interesting question that I want to think deeper into it.

The existence per se is hard to define, but to put it simply, I would consider that a person exists(or have existed) if the person have physically interacted with another person proved to exist. This is because, if a people does not physically interact with any other, then no matter how many references or data we have about the person, we always claim that the person could be a imaginary person that does not physically exist in the world.

In this case, as I am only considering the experience of me, I would not consider the people that actually exist but not necessarily need to exist for the sake of complete my experience with the world(i.e. at any point of time and space I would not interact with the person physically, whether the person exist physically does not affect my world). Hence, the question is simpler now:

Considering that I am an individual, how many people need to exist physically such that the world that I interact with is a completed one?

Now I start with assumptions that are necessary:

• As mentioned earlier, for existence, I would consider that a person exists(or have existed) if the person have physically interacted with another person proved to exist.
• I myself exist.

Then, I can be sure that the people that I physically interacted with do exist, let’s call this group of people group A. Following the first assumption again, the people who have physically interacted with group A do exist, and the group of people that I can be sure of their existence would expand(This idea is linked to the concept of connectedness in graph theory, the link between people would be that they are sure of each other’s existence). Hence, if this process keeps going on, ultimately I will have a group of people such that all the people in the group only interacted with the people that are in the group and no one else. (And this actually corresponds to the idea of closure property in set theory, where the “physically meeting” is a relation that is used to build the set)

This group is now the answer to the question, i.e. this is the group that is needed to complete my experience with the world, but it is a rather vague one, there are issues with the answer.

Issue 1, how can I know if the group is different or the same as the people that actually exist?

For them to be different, there must exist someone that has never interacted with any people that is inside the group. This is actually possible as this group of people is constructed with me as a starting point, if we start with another person who actually exist, then the group may or may not be the same. This would actually mean that there may exist a number of this kind of groups where people inside the group have completely not interacted with any other people in another group. Now the natural question for me would be:

1. Do these groups exist or there will always be one group that contains everyone that actually exist?
2. And if the groups do exist, which group is majority and how can we tell?

The second question is extremely interesting as one person that exists definitely belong to one of the groups, and the person cannot be sure that other groups of people exist, hence, he can claim that  there is only one group and the question is invalid. On the other hand, if the person decides to find out which group is bigger, then the person must first acknowledge that different groups exist, this acknowledgement would also mean that the person must physically interact with a person from another group. This would then lead to two groups merging. (This is not hard to imagine as from this two person, we can construct the two groups again and by linking this two person, the two groups are linked as well.)

To sum up, if we decide to investigate the second question, then we must:

1. Acknowledge that there are more than one groups.
2. We also realize to answer the second question, we would have only one group.

This appears to be a contradiction.

Issue 2, regarding the people who have died, are they inside the group?

There is actually a problem with the issue, by claiming that the people has died, we are de facto claiming that they existed before. Hence, a more proper way to think about it would be “the people who are claimed to have died”.

The apparent answer is yes, if they have physically interacted with someone who exists(which is included in the first assumption). However, we can also consider the case where all the people that have physically interacted with the person, let’s say group B, are all dead. So now the question is are all the people in group B existent(in this case, did they actually exist at some point of time)? This would go on and group B would expand until there is someone, let’s say person C, who have physically interacted with one of the people in group B and the person C is proved to be existent(belonging to one of the groups discussed in issue 1).

The real problem arises when we could not find a person C in a group, i.e. the group consists all dead people. This is rather scary to think about but it may be relevant to the current world. Consider the idea that there are other groups of people(group A), who are sure of each other’s existence, but all of them have died at some point in time. Can others in other groups be sure of the existence of such as group? This idea may be applied to the whole human race in the earth, there may be other human races in which all of them have died before the other race existed. Or the several groups of human races are just physically isolated such that one of them may have no members left in the group before others could discover them.

Okay, that’s enough for this idea of existence, I am not sure if similar ideas are discussed formally in some fields of studies(philosophy or anthropology) but they are just my thoughts, not based on any concrete theories. I like to think a lot.