The Sapir-Whorf hypothesis basically states that there is a relationship between the language that a person uses and the way they think about the world. Although it’s controversial, many linguists believe there is at least some truth in it: as Wikipedia says, ‘The opposite extreme—that language does not influence thought at all—is also widely considered to be false’. The theory has implications, such as that the value of improving one’s vocabulary or learning another language are even greater than they would be otherwise.
The hypothesis has also been extended to programming languages. Essentially, the theory here is that certain types of language are more suited to solving certain problems, and programmers who aren’t aware of these types may not be able to solve some problems in the most effective way. I think this is borne out by empirical evidence: there is a noticeable difference in the way those who have been trained in declarative programming (such as functional and logic programming) solve problems, even in when writing in traditional procedural languages (for example, C), from those who are only trained in those procedural languages. This is important for some types of problem, such as writing compilers or parsers, which are well suited to declarative programming.