Why do we need bodies?

The following scenario is adapted from Keith Laumer's story "The Body Builders": Technology reaches the point that our brains, while still in our natural bodies, can be remotely connected to a synthetic body, which would be as manipulable and would provide as much and as good sensory input as our real bodies. The natural bodies, with brains in their skulls, can be kept in municipal storage, where they will be carefully maintained, exercised and kept trim and healthy, without us being aware of it, because the sensory connections between the brain and the rest of the natural body are severed. It seems the synthetic body could do all the tasks that the natural body could, but would provide two advantages: (a) it could technologically improve on the capabilities of the natural body, say, by providing more strength, agility or sensory data, and (b) one will avoid danger, since one's brain and natural body are safe in municipal storage while the synthetic body goes out into the world of whizzing cars, disease, and all that. Very quickly, one starts to feel about the synthetic body as if one were there, in it—as if it were one's own body.

Question: In a scenario like this, what would we lose? What couldn't we do in this scenario if we did everything through the synthetic body?

One class of activities that we would lose out on are various hobby and sport activities where the contingent limitations of our bodies are important. If various drugs are contrary to good sportsmanship (though, on the other hand, consider the case of Oscar Pistorius), obviously this will be. There can be sports that are played with synthetic bodies. They would in some way akin to remote control car racing. But they would, indisputably, be essentially different sports from the ones we have. (That's part of the point of the Laumer story.)

A second class of acitvities that we would lose out on are ones where physical danger appears to be central to meaning of the activity. Climbing Mt. Everest is a paradigm example. I am inclined to think activities where danger is courted are contrary to the virtue of prudence, since danger is a bad thing. If one could climb Mt. Everest while ensuring safety (e.g., by having a button which, if pressed, would teleport one to a medical facility), one should.

But both of the above classes of activities are pretty much optional to human life. We could get along pretty much fine without bodily sports or mountain climbing: we could still have video games, and cases where non-physical courage is exercised. We would lose out, but we would not lose out on all that much.

In thinking about this, the only cases of activities crucial to the good of humanity that I can think of which could not be done through the synthetic bodies would be:

1. Basic survival functions. (Those would need to be done in municipal storage.)
2. (a) Sexual union and (b) reproduction.
3. The sacraments of baptism, confirmation, Eucharist, ordination and annointing of the sick.

One might think (2a) could be done remotely, and (2b) could be done technologically in municipal storage (extracting sperm and egg, combining them, etc.) But this is mistaken. Sexual union is essentially embodied: the remote "union" would only illusorily be a physical union. And doing (2b) apart from (2a) is immoral—human beings should be the fruit of marital union.

It's interesting that apart from basic survival functions, all of the activities that are both crucial to the good of humanity and that require the natural body are sacraments or closely tied to sacraments ((2) is obviously closely tied to the sacrament of matrimony, as its consummation). It's also interesting that two sacraments are left off the list in (3): reconciliation and matrimony. While currently reconciliation is normally done through in-person confession, I do not think this is essential to the sacrament—I think the Church could change this (I am not saying it would be wise to change it) to confession, say, by telephone. (If general absolution is valid, remote absolution would probably be valid, too, if the Church allowed it.) And while matrimony essentially requires the exchange of consent, this consent need not be given in spoken words (Canon 1104.2), and it is permissible for the two parties to be present only by proxy (Canons 1104.1 and 1105). Still, the consummation must be happen in person for the marriage to be indissoluble.

That, apart from basic survival, all the most important non-survival functions for which a natural body is essential are religious ones or closely tied to religious ones neatly refutes the popular idea that the Christian Church thinks poorly of the human body.