I recently read an article supporting the Sapir-Whorf hypothesis. This was refreshing. Too often I've heard people (always a person who speaks only one language, coincidentally) tell me that language doesn't affect thought.
At first glance, this is a clean, comfortable statement. If language doesn't affect thought, then there is no reason to spend all of the time and effort learning a foreign language, for example. It also fits well in the French and American ideals of equality. Denying that the language we speak affects the way we think protects us from the possibility of linguistic nationalism by claiming that the effect of a specific language is superior to that of another.
The objections to Sapir-Whorf have been given slight approval by the linguistics professors at MIT (though their reasoning tends to be very heavily Western-only, excluding other languages that would contradict their theories) and this is probably one of the reasons that I still hear these objections.
The problem is that it's not true. Language profoundly affects the way we think. Anyone who has been immersed in other cultures will know what I'm saying. Anyone who speaks multiple languages well enough to think in them and dream in them will know what I'm saying. People who have studied a language in school and are at a conversational level may or may not understand what I'm saying.
My wife and I often have certain types of conversations in a specific language. It not only feels more natural, it fits the conceptual model and tone of what we are trying to express. This is not to say that we couldn't express the same concept in English, for example. The question is how much word wrangling would be necessary to accomplish the same task.
A language does not emerge fully formed out of the vacuum. It carries weight and power of a culture's years with it. Its idioms and idiosyncrasies reflect and subtly transmit that culture along with the actual words and phrases that we utter.
In the end, it is good to be proud of one's native language, but a tragedy not to be able to think in others. It's like the world's best painter having only green paint. Sure, he can express any artistic concept on the canvas, but imagine the possibilities if wasn't constrained by monochromatic thinking.