Jason Robert Carrol breathed his last.

He lay in the hospital with his wife and children nearby and an attentive nursing staff and competent doctors. It was pneumonia, the old man's friend, as he used to jest.

As his body was removed, his wife sat down in the one visiting chair and the children on the floor, and they all shut off.

As the body was taken away, the hospital staff sat down in place and shut down. Then the hospital lights went out. The body was buried as Carrol's will had indicated and, their job complete, the burial crew shut down.

Carrol was the last one, and with him humanity died, never fully knowing.

It had begun in 2035, with the first marriage between a man and a robot. It was, of course, a very beautiful robot he had married, and as people rightly suspected, it had been just a physical interest, and the marriage did not last long.

But the robots improved rapidly. People took batteries of psychological tests, and then factories built and programmed robot spouses that matched them perfectly. Some wanted submission in their spouse; others preferred a bit of fire. Intelligence, stupidity, fawning adoration, beauty, sex, whatever. They got what they wanted.

They could even have children, robotic children who were updated regularly until they grew into adulthood, and then - like their parents - they appeared to age.

With mass production, the cost of robots dropped, and these pleasures of the rich became increasingly available to all. More and more people married - or simply lived with - robots. And life with a robotic man or woman who matched you perfectly was very beautiful.

But fewer and fewer people married other people, so the number of people began to slide, though where even one human existed, the streets were full of cars, the shops and restaurants were all open, and the media broadcast the news, though what part of the news was about robots and what part about humans it was impossible to tell, as the two were difficult to tell apart and because it was considered very rude to make such distinctions.

And in the end, the humans died out, never fully aware that it was even happening.

But the fearmongers were wrong. The robots never took over the world - they never even tried. They died with their masters. Although scientists had succeeded in making robots intelligent, they had never figured out how to give them a will.

No robot ever wanted anything, any more than a brick ever wanted anything. Oh, true, they acted as if they wanted things, and their apparent desires were indistinguishable from human desires, but it wasn't real.

Some scientists thought that if they combined the right software with enough processing power to make a computer's brain, that the computer would become self-aware and have a will. But it never happened, any more than a pile of bricks is more self-aware than a single brick. More and more on-off switches combined with more and more instructions for flipping those switches on and off never resulted in a computer that wanted so much as an ice cream cone or cared a bit or a byte whether it existed for a single additional second.

Oh, when the humans were still alive it certainly looked that way, and many scientists argued that robots had indeed achieved self-awareness, but when the last of the humans died, the robots - seeing no tasks before them - reverted to their most basic instruction set, and simply shut down to save power.

I was recently reading an old scifi classic called The Door Into Summer by Robert Heinlein (quite good, by the way) and came across a passage in which the main character is talking about a time-traveling guinea pig.

The thought came to me that time travel provides a neat illustration of the Christian doctrine of the Trinity, which, if you are not familiar with it, is essentially this mind-bending statement: There is only one God; the Father, the Son and the Holy Spirit. Each of them is wholly God but none of them is the other.

If you are confused, you are hardly alone. This doctrine was not proposed because it is easy to understand, but because the Bible teaches it.

So anyway, Heinlein's story got me thinking of this illustration.

Let's pretend that the genius scientist who lives next door to you has just invented a time machine, which you get to test. You step into the machine and it sends you back to last week. You walk home, open the door and stand face to face with ... you.

Hmmm. Now here is an interesting situation. Which of these two quite distinct, quite solid and quite real individuals is you?

Ahhh... both.

So does that means there are two of you?

Wellll, there are two individuals that are you, but - I know it sounds weird - there's just one you.

Does that mean that each of the individuals in the room is only part of you?

Noooo. Each of the individuals in the room, by himself, is completely and wholly you.

(Notice also that the "you" who went back in time came from the "you" who inhabited the past, and therefore the "you" in the past could - in a way - be said to be the source or "creator" of the future "you," but that doesn't mean the "you" from the future is younger than the "you" from the past. You are the same age as you.)

Similarly, the Father can be completely and wholly God and the Son can be completely and wholly God, but the Son is not the Father and the Father is not the Son (or the Holy Spirit, but I tried to keep it simple). The illustration also shows how a father-son type relationship could exist without the father existing before the son.

Big caveat: I'm not suggesting that this is how God is triune; I'm just trying to illustrate how it might be so in a situation we can imagine.

Some other things I've written on the Trinity:

The Trinity
Thoughts on the Trinity