Why am I seeing these grid-like lines in my Minecraft?

So I'm just playing Minecraft, but I'm seeing these lines along the edges of the blocks.
Here's what I mean:

image
image

Here are some things to keep in mind:
1. This happens with AND without OptiFine
2. This happens with any resource pack, even Default
3. This happens on any version of Minecraft, even in Beta and Alpha

I honestly don't know why these lines are here. It's really an eye sore. How do I get rid of them?

Sterling

This is a problem with Forced Anti Aliasing. Or Antisotropic Filtering is on. Try setting your graphics card 3D render settings to "let application choose". Let me know if this makes a difference.

Guest