When expressing in Spanish something that you believed or thought in the past, there are four options:
I learned that creía que was the standard way of expressing this, but I've definitely heard the others. What are the differences between them? In what circumstances can each be used?
Simple answer: all mean the same, "I had this idea in the past".
Long answer: In the context of "I had this idea in the past" in English happens the same, you can choose between "believe" and "think". In Spanish, just use the translation of what you would use in English for that context, it's the same, I guess from indo-european roots. So, for "believe" use "creer" and for "think" use "pensar". (I learned this because I had your same doubt when I had to choose in English between "believe" and "think", so I usually think the sentence in Spanish, and it works.)
About the tense, usually you can use both, it's a matter of context.
Pensaba/creía que vendrías a la fiesta [porque me dijiste que querías verme].
Pensé/creí [en ese momento] que vendrías a la fiesta [pero ya no lo pienso/pensé más].
You use both as the idea is always the same: "I had the idea you would come". For choosing a tense, you need more context, which usually you don't have it. Use imperfecto and indefinido as in situations you would use it (action is finished...).
In a nutshell, if you hear "pensar" or "creer" think them in English. About the tense, you don't have to worry if you don't have more context, always means "I had the idea", and the person talking uses one depending of his/her ideas. If you want to say it, think in English. For the tense, if it's not a situation that is clear which one to choose, then any pick of them and you will be right (I always say creía/pensaba).
Pensé/Pensaba and Creí/Creía are just different conjugations of the verbs Pensar/Creer. The first form (pensé/creí) is preterite simple and the second form (pensaba/creía) is preterite imperfect.
Here's a link that explains it well.
Pensé que me amaba (I thought you loved me) is as valid and has the same meaning as saying Pensaba que me amaba, for example.
The link referenced has this to say:
The preterite [simple] tells us specifically when an action took place.
The imperfect tells us in general when an action took place.
At first, the comparison has to be between "creí + pensé" versus "creía + pensaba".
As for regular and daily usage, creía and pensaba are more common when you are talking about the past.
And for the difference:
Creer is to believe and pensar is to think. The former is more intuitive, the latter is more cerebral.
Creí and Pensé are past preterite forms and refer to what you believed or thought at a single POINT in time, in the past.
Creía and pensaba are past imperfect froms and refer to what you believed or thought over a PERIOD of time, in the past.
For Example:
- Creí X en el ano 2000. => I believed X in the year 2000.
- Creía Y cuando era joven. => I believed Y when I was young.
Without getting too much into proper grammar the simplest way to describe them would be:
Having "Creer" / Believe (verb) as
- Have something plausible or truthful about something that might not be proven otherwise.
- Trust in someone.
- Think, judge, suspect something or be biased by it.
Example:
- Creí que => When you have something for certain; you are expressing your opinion on a situation /thought that already has happened.
- Creía que => Your judgment or opinion about something were changed by someone / something that made you change that believe.
Thinking or having the feeling that something is in a certain way, might not be the same as the process of the mind to think and it is used the same way as "creer" "creía" forms.
The thinking as used in a believe form is more like the gutsy way, not the actual brains / neurons (or the process of thinking ) doing what they're supposed to do.
Hope made myself clear Greetings.
