Well, if they want to build something, they get many bricks and build 1 buildings. If they want another one, then they build 1 more and have many. They build them until they have 0 homeless people. Then they have 1 big party, drink many shots, and give 0 @#$&s.

@MishaR: so dimension for 1 brick is 1 cubic centimetres

I prefer to think of it as a 0m cube, but sure.

To post this very question you are using just 0 and 1...

@L.Dutch: they invented 0 which is important in math, and more than 1 is many which is also important too.

There is already humanoid species on an Earthlike planet with exactly the limited numeracy that engineered transportation & buildings. It's our species, & our planet. It's what we did in the historical past. Look at our technological history.

0, 1, many. Many 0, many 1, many many. Many many 0, many many 1, many many many. Many many many 0, many many many 1, lots.

I can't help to imagine, how it's possible for inteligent species to NOT count above 1. We even taught dogs and other animals to count higher. Why they would even stop counting past one? If they see two things, it's clearly 1 thing and 1 thing, and its clearly different then 3 things, so why to call it same, when it could be lifesaving knowledge?

@L.Dutch-ReinstateMonica but peoples who invented stuff to post this question used much more then solely 0 and 1...

@SRM Humans can only perceive up to four!

@SRM which gives us the naming of "Fiver" which was literally translated to "Little Thousand" - the most charming footnote I've ever read in any book ever (and I've read at least five books... :) )

Do you mean sentient? Sapience refers specifically to being a "deep thinker" or such.

@user253751 I forget how limited the rest of you are. ;-)

My alien race (the Eulerians) can only count 0, 1, e, pi, and i.

@DrSheldon: I want nothing to do with them. They start out reasonably enough, but in the end I fear they're irrational.

"Assuming they are capable to count using 0, 1 and many" - if they are sentient, then they will learn to count higher when the need arises. Being sentient means being able to learn, and to discover new things. I'm sure that people born in primitive tribes, which don't use numbers besides "0, 1, many" are perfectly able to learn a different numbering system if someone teaches it to them (as the limitation is more linguistic and cultural rather than genetic). Even animals can be taught to count, so a sentient species capable of building a civilization should be able to as well.

@vsz: look up number sense in animal but ignore clever hans ;D

@user6760 : I wasn't referring to clever Hans. Crows can count to more than one. And a sentient species capable of complex language and of building transportation surely would be able to. If they didn't have it before, out of cultural reasons or due to the lack of need, they will develop one when the need arises.

If you look at e.g. unicode.org/cldr/charts/34/supplemental/… you will find that real existing humans had the exact same issues once upon a time (such as the Czech or Croatians, there is "1", "few" (2-4), and "many"). Others (English) still hint to it on ordinal numbers: first, second, third, anything-th. Hebrew is similar, you've got one, two, and many (20+), and not-many in between. Irish is even crazier, they've got 4 or 5 different kinds of few/many. Obviously, being limited in counting is no permanent hindrance to survival or development.