Phrase or idiom for only having seen one part of something but not the whole thing?

Question

For example, suppose I am a student studying physics, and I've taken a bunch of theoretical classes in electromagnetism, quantum mechanics, particle physics, etc. But I have not done any experimental physics, which some would argue is also integral to a physics education.

How can I complete a sentence along the lines of:

Although I enjoyed learning the theory, I knew I was missing [not exactly sure what to put here, but I want to say that experimentation is like the "missing half" in my physics education].

Thanks!

Answer 1

Although I enjoyed learning the theory, I knew I hadn't seen the whole picture, because I lacked experimental courses.

the whole picture (idiom)

The overall sense or presentation of a situation, concept, topic, etc., including all related factors and potential consequences. You're focusing on one small part of the negotiation, but you need to see the whole picture—we may need to compromise on a few items to get the best deal in the end. Farlex Dictionary of Idioms

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The function of university research was initially relevant for W. von Humboldt, because the assumption was that only someone who occupies themselves on a daily basis in verifying theories and discovering new truths can see the whole picture in a particular field... Aleksander Kobylarek; The Polish Humboldtian University in the Face of Paradigmatic Change

Answer 2

You call somebody a "frog at the bottom of a well".

It is a famous Chineses idiom that is stated when somebody is making seemingly confident assumptions but from another's perspective they are just ignorant.

It is almost always used in a derogatory manner.

"You’re a frog at the bottom of a well" means you have a narrow viewpoint … that you think the sky you can see out of the top of the well is all there is to the world.

Used in your sentence you could say:

Although I enjoyed learning the theory, I knew I was merely a frog at the bottom of a well.

Frog of the well

Answer 3

I have greatly enjoyed studying theoretical physics but experimentation is the lifeblood of science and I feel that without that I am really studying only half the subject.