In one of the earlier posts in the Kanji section of the forums, I've read that there are tons of Kanji to learn and that learning more Kanji is an on-going thing. But in one of the earliest lessions of Rocket Japanese, I've read the part where it says that when Kanji was the only thing the Japanese had, they invented Hiragana and Katakana to simplify the language. Why go through the trouble to invent Hiragana and Katakana to simplify the language if Kanji is still used and will always have new ones to learn in the first place?

Excellent question. As a Japanese myself, I am not sure if I can answer that question properly - why did we go through the trouble of creating 2 more sets of alphabets when Kanji would have done it all? Well, my first guess is that Japanese people are good at adopting and adapting - by this I mean that they like to adopt foreign knowledge, skills, even food! and adapt it to their own culture - make is "Japanese". I believe the Japanese TEMPURA originally came from Portugal!! or somewhere in Europe. But now it's one of the main Japanese dishes. Back to Hiragana and Katakana - it is true that Kanji used as common as Hiragana and Katakana - but in general, Hiragana and Katakana are easy compared to Kanji and those are the first alphabets children learn in school. If you have a good understanding of Hiragana and Katakana it is easier to learn Kanji - as Hiragana and Katakana originate from Kanji. What makes Japanese unique is the ability of combining Hiragana, Katakana and Kanji and differentiating a foreign word (English-loan word) from a Japanese word, or differentiating from a noun and a particle. If everything was written in Kanji, it would quite difficult to point out which word is a particle and which is part of a noun. -Hope that helps! Sayaka :P

In other words, if I understand this right, it's like in many european languages where we use big and small letters. We don't do it because we need to, but it makes the language more challenging and more rewarding. That is if we are able to adapt the rules.