How we cite our quotes: (Book.Chapter)
Quote #1
'All is as thinking makes it so.' The retort made to Monimus the Cynic is clear enough: but clear too is the value of his saying, if one takes the kernel of it, as far as it is true. (2.15)
This is a foundational concept for Marcus. It helps him to define his understanding of the more problematic things in life: pain, wrongdoing, and hindrances. He sees that these problems exist in the world, but that each man can take away the sting by getting his mind in the right place. Instead of passing judgments on the things that happen—thereby assigning them negative values—he can remain disinterested and analytical, seeing the wrong for what it really is. This allows him to turn each hindrance to good use, since his reason is not muddled with emotion.
Quote #2
Everything in any way beautiful has its beauty of itself, inherent and self-sufficient: praise is no part of it. At any rate, praise does not make anything better or worse...Does an emerald lose its quality if not praised? And what of gold, ivory, purple, a lyre, a dagger, a flower, a bush? (4.20)
Marcus remarks on the supreme indifference of the empirical world. You can't make a beautiful gem anything but what it is by talking smack about it. The same is true of people. This is a part of reality that isn't negotiable: virtues are what they are—no further judgments necessary.
Quote #3
Harm to you cannot subsist in another's directing mind, nor indeed in any turn or change of circumstance. Where, then? In that part of you which judges harm. So no such judgement, and all is well. (4.39)
This is part of Marcus's "thinking makes it so" campaign. Wrongdoing is entirely subjective: it can only work on a person if that person feels wronged. Think of it this way: if the ax of the wrongdoer cuts down a tree in the forest and nobody is there to hear it fall, nothing bad has ever happened to that tree. Right? But seriously, Marcus reminds himself time and again that it is up to him to retreat into the "fortress" of his mind rather than respond emotionally to unpleasant things that may be happening.