[ Charles wants to protest. What's the point of knowing some of the future but not all of it? The things Erik wants to keep him ignorant about are clearly important events -- why else would he withhold them?

If Charles were slightly less ethical, the point would be moot. He could simply look at Erik's memory in its entirety, and Erik wouldn't know he did it. Charles only puts his fingers to his temple as a politeness, a gesture to alert other people that he's using his ability. Without that, he could be as silent as a thief. But, no. To do so would be to betray Erik's trust-- however much of that he currently has, in the future Erik is from. ]

Understandable. Slightly regrettable, but understandable.

[ Erik could just tell him. It would be easy enough, if incredibly slow and undetailed. But Charles wants to see it. He wants to understand it in the language he knows best. ]

I'd prefer to see your memories, if you don't mind. [ Charles says it delicately, because frankly, he's not sure if Erik will mind or not. He hadn't had that helmet on the last time Charles contacted him, but he's not sure if that's a welcome. ] Anything you don't wish me to see, you can hide behind a metaphorical locked door, and I won't go snooping. I can show you how, if you like.