Can somebody see a message without the other person knowing that they saw it?

[Matt]

on facebook

[Charles]

probably delete the message then it might not tell seen time.

[Severos]

depends, if you mean while chatting it's not possible i believe
however if it's just a normal message, you can go to message center and select the conversation, then there's a action button, click it and you'll see a mark as unread button.

[kyswagga]

There are a few ways. If the message is short enough (one line) that they can read without clicking on the message is one way. If a person doesn't click on the message it will show unread. Also, if the delete the message it won't show that it has been read. If they block you after reading you will never know if it was look at or not.