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Why do viruses attack other cells? They are not alive, so how do they know what they want to do?
Question Date: 2005-10-24
Answer 1:

That is an interesting question!
Philosophers have wondered for a long time what it means to be alive, and to be conscious or sentient. Although of course nobody can know what it might be like to be a virus, we can certainly gain strong clues to the answer through the things we know from science, philosophy, technology, and personal experience.

In biology we dein order to be considered alive an organism must be able to survive, adapt and respond to its environment, and reproduce on its own. By this definition a virus is probably not alive, since it really doesn't have the ability to perform important biological processes such as reproduction without taking over another cell.

However, this definition of living is not always satisfactory in a non-scientific sense. Many philosophers may argue that this is not a good definition, because just because something needs help from something else doesn't necessarily mean its not alive-- after all, don't we all need help of some sort to survive? So, to a philosopher being considered alive may be more a question of consciousness than of biological processes.

For example, people used to think of animals as automatons. According to the scientific definition, animals were certainly alive. However, people doubted that they had any consciousness. They thought that animals didn't really think or feel emotions, they just responded to things based on instincts. Because of this, animals didn't have any rights and a lot of people didn't care what happened to them at all. Of course, if you have any pets I think from your own personal experience you would disagree with this!

Science, philosophy, and personal experience have all now come to the conclusion that, while an animal is not as smart or emotionally complex as a human, certainly animals do learn, make choices, and experience pain and suffering and all forms of emotion. The fact that people didn't acknowledge this earlier was more because of prejudice and a lack of understanding about what it means to be an animal.

This raises a question: What other organisms might experience things that we just don't recognize? Do plants experience some form of consciousness that we don't understand? What about bacteria? And, like your question, what about even things that may not really be alive, like viruses?

So far, the answer to these questions is a strong no. All of our evidence suggests that in order to have any form of consciousness at all an organism must have certain organized biological structures that all of these organisms lack. In the case of a virus, its particularly clear, because a virus really lacks any form of independence whatsoever. So, the answer to your question is that, because a virus has no consciousness, it actually does not make choices, or have knowledge, or goals-- it actually does not know what it wants to do!

So, if a virus can't know what it wants to do, how does it do things? Think about all of the technological devices you have in your home and school, and how they work on their own. Your alarm clock keeps the time, and makes a noise to wake you up at just the right time. Your refrigerator or home air conditioner turns itself on or off to maintain just the right temperature. Your answering machine can tell when somebody calls, and then answers the phone and records a message. If you were an alien who saw these things for the first time you might think these were the living creatures that inhabit the earth! Butdo any of these devices do what they do because they want to? You will say of course not, they are just following a program, doing what they were built to do.

Viruses are very similar! They are relatively simple biological devices that just simply follow a program, doing what they are built to do, though instead of being electronic or mechanical they are genetic in nature! Actually, this is why we also use the word virus to explain small sneaky computer programs that spread over the internet and cause problems. Computer viruses aren't alive or conscious either, but they certainly behave just like biological viruses, spreading from one computer to another and causing damage!

Did you know that your body is full of even more complicated cells that behave by just following programs? Every day you do things that are the result of conscious choices: you eat something for breakfast, you go to school, you talk to your friends, you do your homework (of course), you read a book. However, your body is doing millions of things you aren't even aware of! Your heart is beating, your lungs are breathing, your muscles are contracting and relaxing, your immune system is fighting infections, your digestive system is extracting nutrients from food, etc. All of the cells involved in those processes are just doing what they are genetically programmed to do, without any thought whatsoever.

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