by (method, agent) and with (tools, etc)

The difference

By and with can both be used to say how somebody does something, but there is an important difference.

We use by to talk about an action – what we do to get a result. We use with to talk about a tool or other object – what we use to get a result. Compare:

• I killed the spider by hitting it. (Note the -ing form after by.)
  I killed the spider with a shoe. (not … by a shoe.)
• ‘I got where I am by hard work.’
  ‘No you didn’t. You got there with your wife’s money.’

Without is the opposite of both by and with in these cases. Compare:

• I got her to listen by shouting.
  It’s difficult to get her to listen without shouting.
• We’ll have to get it out with a screwdriver.
  We can’t get it out without a screwdriver.

By is also used to refer to means of transport (by bus, by train, etc), (see here).

Passive clauses

In passive clauses, by introduces the agent – the person or thing that is responsible for the action (see here).

• I was interviewed by three directors.
• My car was damaged by a falling branch.

We generally prefer with to refer to a tool or instrument used by somebody. Compare:

• He was killed by a heavy stone. (This could mean ‘A stone fell and killed him’.)
• He was killed with a heavy stone. (This means ‘Somebody used a stone to kill him’.)