Thinking and feeling with と思う and と考える

The verbs 思う and 考える are both commonly translated as "to think". However, while 考える relates to a more methodical/analytical type of thinking, 思う focuses more on the (sometimes involuntary) feeling of thoughts that kinda float in someone's mind. You can think of 考える as "consider" or "evaluate", although not always as serious.

We already saw the と particle used to quote thoughts in Lesson 30. Review that lesson if you forgot it. 考える works in the same way.

何かトラブルがあったと考えるのが普通だろう。
I guess it is normal to consider that some trouble might have happened.

Focusing back on と思う, the basic usage is that of a simple thought or feeling. It normally means that the speaker thinks something.

来たと思った 
I thought he came.

This thinking is often natural and unplanned.

A quirk of the verb 思う is that when we talk about other people, the verb is usually in ている form instead. In this usage, it can imply there is some reason for us to assume something about someone else’s thoughts (maybe they voiced their opinion out loud).

彼は本気でそれが正しいと思っているのだ。
He genuinely thought that was right.

Lastly, when と思う is used with a volitional phrase, it means that the speaker is considering doing something. In this usage, it is similar to たい, but it is more concrete and focused on actual relatively short-term planned actions rather than a state of desire.

食べようと思う
I think I will eat