The word "scientific" is perhaps the word which is the most associated with "hangeul", but is it really scientific? Well, as a linguist, I have to say no, it's not scientific.
Having myself thought about the word "scientific" a lot and about its definitions, I think that a lot of people use the word "scientific" to mean "good" or "correct" in opposition to "unscientific" meaning "bad" or "flawed". As a linguist, I know two things:
-everyone has his own "mental" dictionary and world visions and different words mean different things to everyone
-In linguistic terms, no writing system has ever been, and will ever be, scientific.
We linguists frown upon the use of the word "scientific" for any writing system. In fact, while most Korean linguists have been told that hangeul was scientific since they were kids and write that in their dissertations and papers, linguist Robert Ramsey, a specialist in Korean language, has avoided the use of the word scientific to describe hangeul.
What linguists say in order to avoid offending Koreans is that hangeul is a great thing because it provided an "easy" alphabet to educate the masses. Well, I wish that were true. Hangeul was invented in the 15th century, and in 1950 only 22% of the Korean population knew how to use hangeul, an alphabet that I, like most foreigners, learned how to use in 2 hours. By this I don't mean that 50 years ago Koreans were stupid, but I mean that while spoken language is vital and acquired by all human beings without having to be taught, writing requires years of training among children to be mastered fully.
So why isn't hangeul scientific? Linguists know that writing is a "bastardized" form of speaking and that writing systems fail to transcribe sounds in an exact way. Different people pronounce sounds differently, sounds evolve, and there is more to than just letters, there's intonation, pitch, length of sounds etc. In fact, the letter ㅅ can be pronounced "s", "sh" or "t" depending on where it stands, ㄱ "k", "g" or "kh" depending on where it is. Not so scientific indeed.
But there's a reason people call it scientific though. In fact, Korean language has something in its sounds that many other languages don't have: words are pronounced differently depending on whether there's a vowel, consonant or nothing preceding the word. 가다 ("to go") will be pronounced "kada" but if you ask someone "where are you going?" you'll say "odi Ga", but it's the same ka as in kada. So the alphabet had to take this relationship into account and therefore drew letters that could represent several sounds at the same time.
Some Koreans are trying to export hangeul, but this would require adding a significant number of letters to make it exportable. Let's say we used hangeul for English. would "cap" and "gap" be spelled the same way? What would be scientific about that?
I would add that there's a difference between knowing an alphabet and actually reading. While foreigners easily memorize hangeul as an alphabet, all sorts of complicated rules make it difficult to read. Of course, those who were trained since they were kids will know the rules, just as those who were trained to memorize Chinese caracters or kanjis since they were kids will learn how to use them properly.
The point is linguists have stopped searching for a scientific way to codify language and have agreed that writing, in any form, is a misrepresentation of speaking. While hangeul may be called scientific for political reasons, may have been voted "scientific", if it were really scientific, no voting would be needed, just as doctors don't vote to determine whether patients have cancer or diabetes.