@PaxDaga: Not now. I cannot teach you the proper mechanism for definitions until you know basic FOL, because it depends on FOL. Since you said you wanted to learn FOL from me, let me tell you where to start. I'll teach you the same way I taught F.Zer and Prithu in this room, starting from PL. For PL, read and make sure you understand the first few sections up to "Boolean operations" in this post.