There was a similar question posted a couple of months ago, but the details of what that person was looking for are a bit different from mine. I am looking for another saying that describes you being unable to have one without the other. Two sides to a coin is one, and someone mentioned "you can't make lemonade without lemon and water." The two entities that I am trying to describe are very different on their own, but fuse into its own entity when together. Any ideas? Thanks!
'Two sides of the same coin' does not quite mean what you describe.
two sides of the same coin - different but closely related features of one idea
It essentially means that two things are the same. I might use it in a context where someone is describing someone else as both 'lazy' and 'messy' and in response I could say that those are 'two sides of the same coin' and thereby suggesting that they are one and the same, in this case suggesting that the person is messy because they are lazy.
As far as I can tell you want a pithy phrase to describe two things that are good together but not necessarily either good or as good apart.
I'd suggest a simile in this situation. A very common type of phrase is to say:
[Something] without [something] is like [something else] without [something else].
Currently on the London Underground for example there is an advert that says something along the lines of 'a woman's hair without product x is like rock without roll' (the latter part usually a ridiculous separation for humour value). There's no standard phrase used here but it's an opportunity to be creative.
A couple more examples:
A man without ambition is like a bird without wings (from a 1908 business magazine)
A house without books is like a room without windows (a proverb that goes back even further)
- You can't make an omelette without breaking some eggs.
- You can't have a picnic without ants.
- Seek first to understand. Then to be understood.
- There are two kinds of people: those who believe there are two kinds of people, and those who don't.
- There are two kinds of people: those who finish their sentences,
- There are two sides to a coin: "Heads I win and tails you lose."
Some of my originals:
- There are two sides to every coin but that has nothing to do with solving any real, complicated problem.
- You can't have duality without duality.
The closest idiom I can think of to your requirement for something that requires two elements is:
It takes two to Tango.
There is no dance without two different participants.
"No rainbows without rain." -- not an idiom, but idiomatic.
Also, by the way, the "two things fuse to something very different than constituent parts" is what is meant by the word "synergy"/"synergistic", and by the expression "more than the sum of its parts".
"There are two sides to every coin" means you can't have the good part of something without its bad.
You could say : "if you want to have your face in the light, you should have your back in the dark".
"Two sides of the same coin" has a different meaning : 2 things seem different, or opposed but boths are the same actually. You could say democrat and republican politic leaders are two sides of the same coin for example.
A few coined phrases showing two sides
You have to take the good with the bad.
Don't fly higher than you're willing to fall
Don't invest more than you're willing to lose.
"double edged sword"
Technology is a double-edged sword. It has its goods and its bads.
Merriam-Webster defines "double-edged sword" as:
something that has or can have both favorable and unfavorable consequences