I'm a contractor at this company, and I see a colleague who is slacking in his job. Do I tell his manager?

You should try to confront the colleague directly first. Talk to the manager at last resort. If you go right to the manager it's just going to make you look bad.

Only tell the manager if it affects you directly.

If someone is doing poor quality work at a construction site or medical organization it could be dangerous, if someone is slacking off when they should be doing data entry it could just be a pain. If the former I would go to the manager ASAP. If the later I would consider talking to the person vs. not saying a thing at all.

Now there are a few considerations. Does the person you are thinking of reporting have more than casual contact with you? Can he/she impact your position as a contractor?

Do you feel like you can give that person constructive criticism? Has anyone else noticed or mentioned this? You have 3 options, 1- Don't say anything 2- Tell him/her 3- Tell his/her boss I would quickly jot down the pros and cons of each to help you decide.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.