to think something over: to consider, weigh, and form a judgment in the mind
At its root this word is about the work the mind does when it turns something over. A person stops, takes account of what is in front of them, and reaches a conclusion. The same act can be quiet reflection on one's own life or a quick read of someone else.
The verdict the mind settles on can be honest pondering, a guess that turns out wrong, or a judgment passed on another person. In every case the action is internal: a settled estimate, not yet an outward deed.
This bare consider sense shades naturally into the others. Once the mind forms a verdict it can credit a value, aim at a plan, or work out a design. The line between thinking and the rest is whether the conclusion stays a private opinion or moves toward an outcome.