If I could express the same thing with words as with music, I would, of course, use a verbal expression. Music is something autonomous and much richer. Music begins where the possibilities of language end. That is why I write music.
In his work a means of escape has been found from outmoded romanticism on the one hand and from a barren objectivity on the other.
Neville Cardus in the Manchester Guardian, 1935; reprinted in his The Delights of Music (1966) p. 56.
Sibelius is unquestionably a leader in the front rank of symphonic composers. He has got out of the ruts worn by his predecessors far more completely than Brahms got away from Beethoven, or even Richard Strauss from Wagner. If someone would only burn Finlandia he would come to our young people as an entirely original inventor of a new art form and a new harmony technique.
Sibelius has an acutely developed sense of identification with nature and a preoccupation with myth that at one and the same time define his unique strength and his basic limitation. These preoccupations override his involvement in the human predicament, except in so far as it affects man’s relationship with nature.
Robert Layton Sibelius (London: J. M. Dent,  1971), ch. 16, p. 153.