Discipline: to practice or to punish?

Since Silas bit a child yesterday (poor Vivian!), I have been thinking a lot about discipline. What is discipline really? What does it require? Does it require some kind of pain or harshness to separate it from regular conversations? Since we cannot reason with a one or two or three or even ten year old necessarily, we must do something else to discipline. For discipline to exist, there must be an authority figure who is imposing his or her authority on someone else-- what does that look like?

The most polite and well-mannered children I know are spanked (this is a sampling from a small pool). I, however, strongly dislike the idea of hitting a child to teach him what is wrong and to enforce what is right. Is it silly, though, to refuse to spank on principle of imposing force/violence but to grab a child by his arm so it hurts or to squeeze his hand? Aren't these the same things, forms of pain for effect?

Must there be a physical element to discipline for it to be effective? Must that physical element be painful in someway? If there is not a physical element, is that replaced with shaming or emotional pain?

I don't know the answers. I do know, though, that it could be easy for me to act out of anger, so as I am thinking about this, I want to consider boundaries for myself too (i.e. no hitting). I also have seen how easy it can be to shame children (and adults) and how damaging that shame can be. What are the wise ways?

In the American Heritage Dictionary, Discipline (which comes from the same route as disciple -- not usually how we think of it) is defined as follows:
1. training expected to produce a specific character or pattern of behavior
2. controlled behavior resulting from such training
3. a state of order based on submission to rules and authority
4. punishment intended to correct or train

verb:
1. to train by instruction and practice
2. to punish

The primary meaning in both the noun and verb is training and teaching that involves practice and controlled behavior.
The punishment is secondary.

I wonder how we best train and teach and produce upstanding and outstanding children? And I wonder how I will figure it out...