An infinitive is the base from of verb plus

An infinitive is the base from of verb plus TO

to go

to see

to write

1. He believed education was important (thought)

2. He thought fathers ought to set an example (action)

3. I think there is something about bullies, but I don't remember the details of how he handled that. (action)

4 you could find something he said to the school board about what he believed. (speech)

Hoped I helped