Is it really possible to make a pact with an AI player? They always seem to refuse. Furthermore, what do the pacts do? I can't find it in the manual or Great Library.
The manual does explain what those pacts mean and what you will benefit from them, etc. Honestly, I haven't successfully singed any pacts with any AI player without threatening to declare war on them. I think if you're strong enough, you can just threaten your way through, and even get an alliance with the AI.
Yes, you must be strong .
As the proposal come from your side you shoul give additional arguments. For example I proposed alliance to French and attached a little gift of 15000 gold to proposal. They agreed.
It is very helpful if you are able to increase your prestige in foreign civilization first (e.g. using diplomats).