Spatio-temporal Contiguity
In the previous section, we asked what made a person the same person over time. We did not make the customary distinction, at least initially, between persons and non-persons. We preferred to make the distinction between types and tokens. In this respect, we concluded that what makes a type the same type over time is continuity. We decided that continuity theories can explain what makes a type the same type over time. They cannot, however, explain what makes a token the same token over time. This naturally enough raises the question of what does make a token the same token over time. When we answer this question we will have two different accounts of identity over time: one for types and one for tokens. This will put us in a better position to judge whether we are our type or our token. In this section, I will explore the issue of what makes a token the same token over time.
The first and most obvious question to ask seems to be, how can you tell which token you are? Again, I will not distinguish between persons and non-persons here. The question could be rephrased in terms of a chair. When you are faced with two different tokens of the same type of chair, then how do you know which is which? I don't think that there is anything tricky about a question like this, since the answer seems obvious enough. You can tell which chair is which because of its position in space-time. Suppose that my work mate has exactly the same type of chair that I do. Even if this were the case, I would still have no difficulty at all determining which chair was mine and which was his. For one thing, my chair is at my desk and his chair is at his desk. If one wanted to be any more precise than that, one could map the precise spatial co-ordinates of my chair as opposed to his based on some agreed-upon co-ordinate system. Different tokens might occupy the same space at different times. But they cannot occupy the very same space at the very same time, without being the very same tokens. Hence, spatio-temporal co-ordinates determine the identity or difference of tokens.
But then what makes a token the same token over time? We have already decided that position in space-time is a factor in determining the identity of tokens. But the same token must occupy many different positions in time by definition to be the same token over time. Additionally, the same token may presumably occupy many different positions in space over time. We might again consider the example of a chair. I can move my chair from one part of the room to another over the course of fifteen seconds. And I consider that it has been the same token that I have been moving all that time. The only way it seems to me that I can determine this, is that in each case, its spatio-temporal location has been contiguous. In the same continuous stretch of time, we can see a chair with co-ordinates that change only slightly from one moment to the next. We use spatio-temporal contiguity to determine what makes the token the same token over time. This seems to hold true for our observations of backed-up persons. The backed-up person and the restored person do not have spatio-temporal contiguity with each other. That enables us to determine easily that they are two different tokens.
Does spatio-temporal contiguity provide a full account of the identity of tokens over time? It somehow seems too superficial an account. For example, when I move a chair across a room, I know it is the same token in a way deeper than that it has spatio-temporal contiguity. I know it because I am actually moving it. That is, I am transferring it across space, while it is naturally transferring itself across time. It is the transference of the chair across space and time that is what gives it its contiguity in space and time to begin with. The transference is the essential part of the tokenhood across time, and the spatio-temporal contiguity is merely incidental.
Let us test this intuition further. Is the issue of spatio-temporal contiguity really different from the issue of transference? To answer this question, let us ask, can something be transferred across space and time without being spatio-temporally contiguous? Let us imagine that there is a part of the room with special powers. If I move the chair to this part of the room, then the chair suddenly disappears from that place and reappears on the other side of the room. That establishes spatial discontiguity. To provide temporal discontiguity, imagine a pause between the time that the chair disappears in one part of the room and reappears on the other side.
Let us now substitute a person for the chair. We can imagine two person-stages, one at the special point of the room, and the other at the other side. The first person-stage goes to the special point and abruptly disappears. Ten seconds later, another person-stage appears on the other side of the room, and says, "Wow, that was a blast, can I do it again??" The two person-stages have full qualitative continuity with each other. That is, they have continuity of thoughts, memories, body and so on. This is enough to establish that they are the same type of person, as discussed above. But in order to be the same token of person, there has to have been a transference of that token from one part of the room to the other. There is an obvious lack of spatio-temporal contiguity between the two person-stages. But is this enough to show that there has not been a transference of the same token across the room?
I'll leave you on that cliffhanger until the next section...
The first and most obvious question to ask seems to be, how can you tell which token you are? Again, I will not distinguish between persons and non-persons here. The question could be rephrased in terms of a chair. When you are faced with two different tokens of the same type of chair, then how do you know which is which? I don't think that there is anything tricky about a question like this, since the answer seems obvious enough. You can tell which chair is which because of its position in space-time. Suppose that my work mate has exactly the same type of chair that I do. Even if this were the case, I would still have no difficulty at all determining which chair was mine and which was his. For one thing, my chair is at my desk and his chair is at his desk. If one wanted to be any more precise than that, one could map the precise spatial co-ordinates of my chair as opposed to his based on some agreed-upon co-ordinate system. Different tokens might occupy the same space at different times. But they cannot occupy the very same space at the very same time, without being the very same tokens. Hence, spatio-temporal co-ordinates determine the identity or difference of tokens.
But then what makes a token the same token over time? We have already decided that position in space-time is a factor in determining the identity of tokens. But the same token must occupy many different positions in time by definition to be the same token over time. Additionally, the same token may presumably occupy many different positions in space over time. We might again consider the example of a chair. I can move my chair from one part of the room to another over the course of fifteen seconds. And I consider that it has been the same token that I have been moving all that time. The only way it seems to me that I can determine this, is that in each case, its spatio-temporal location has been contiguous. In the same continuous stretch of time, we can see a chair with co-ordinates that change only slightly from one moment to the next. We use spatio-temporal contiguity to determine what makes the token the same token over time. This seems to hold true for our observations of backed-up persons. The backed-up person and the restored person do not have spatio-temporal contiguity with each other. That enables us to determine easily that they are two different tokens.
Does spatio-temporal contiguity provide a full account of the identity of tokens over time? It somehow seems too superficial an account. For example, when I move a chair across a room, I know it is the same token in a way deeper than that it has spatio-temporal contiguity. I know it because I am actually moving it. That is, I am transferring it across space, while it is naturally transferring itself across time. It is the transference of the chair across space and time that is what gives it its contiguity in space and time to begin with. The transference is the essential part of the tokenhood across time, and the spatio-temporal contiguity is merely incidental.
Let us test this intuition further. Is the issue of spatio-temporal contiguity really different from the issue of transference? To answer this question, let us ask, can something be transferred across space and time without being spatio-temporally contiguous? Let us imagine that there is a part of the room with special powers. If I move the chair to this part of the room, then the chair suddenly disappears from that place and reappears on the other side of the room. That establishes spatial discontiguity. To provide temporal discontiguity, imagine a pause between the time that the chair disappears in one part of the room and reappears on the other side.
Let us now substitute a person for the chair. We can imagine two person-stages, one at the special point of the room, and the other at the other side. The first person-stage goes to the special point and abruptly disappears. Ten seconds later, another person-stage appears on the other side of the room, and says, "Wow, that was a blast, can I do it again??" The two person-stages have full qualitative continuity with each other. That is, they have continuity of thoughts, memories, body and so on. This is enough to establish that they are the same type of person, as discussed above. But in order to be the same token of person, there has to have been a transference of that token from one part of the room to the other. There is an obvious lack of spatio-temporal contiguity between the two person-stages. But is this enough to show that there has not been a transference of the same token across the room?
I'll leave you on that cliffhanger until the next section...
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