In 1830, the Romantic movement in music was in full swing. Hector Berlioz wrote his Symphony Fantastique and his program notes describe the symphony as a musical expression of his inner feelings – quintessential Romanticism, and so like a style 4.   His notes reveal several important things about a Four’s inner workings. I include some of his actual program notes. Then I’ll explain why it is so “fourish.” (He is, at that time, madly, hopelessly in love with an actress he has yet to meet).
The author imagines that a young musician, afflicted with that moral disease that a well known writer calls a “wave of passion,” sees for the first time a woman who embodies all charms of the ideal being he has imagined in his dreams, and he falls desperately in love with her. Through an odd whim, whenever the beloved image appears before the mind’s eye of the artist, it is linked with a musical thought, passionate but at the same time noble and shy, he attributes to his beloved. The image and the model it reflects pursue him incessantly like an idee fixe. That is the reason for the constant appearance, in every movement of the symphony of the melody that begins the first allegro. The passage from the state of melancholy reverie, interrupted by a few fits of groundless joy, to one of frenzied passion, with its moments of fury, of jealousy, its return of tenderness, its tears, its religious consolations–this is the subject of the first movement.

This passage illustrates a number of Four characteristics: the intense emotional inner life, the dramatic mood swings, something we technically call “synesthesia”–the sensory expression in more than one sense of an emotion, seeing an object or idea and hearing a sound or even getting a taste of the object. I think only (or at least mainly) Fours do this.
Berlioz was in despair over his unrequited love (He hadn’t MET her yet!) but like a good Four, he turned his suffering into art, in this case, a glorious symphony.