Yes, they are both correct. They're often interchanged, but the first is more often used as a general comment or statement. The 2nd can be used for this as well, but as well it is used when you have been discussing a topic and you want to make a point that the 'truth' will never be known. So, they can be interchangeable but the 2nd is often used when you're making a point, rather than a general statement. But really, the two are so close to being the same, you can probably treat them as the same.