Believe / Think / and IMO are all synonyms for me.
I am not religious. They are just my current thoughts based upon the information I have. They are ever changing.
So when I say believe I am not speaking like a religious person and implying undoubting faith.
good man.
Unfortunately 'believe' has religious connotations for most people.
It's a hijacked word.
I try to use something else such as "I am convinced that..."
or something similar.