"[T]he sea is only deep when it is pure, and only pure when it is transparent: as soon as it is impure we no longer see its depth but only its surface, and if we see only its surface, that means it is not transparent. When, however, it is deeply and transparently pure, then it is at one with itself, no matter how long one looks at it; then its purity is its abiding unity with itself. And for this reason we liken the heart to the sea, because its purity is its being abidingly deep and transparent. No storm may disturb it, no squall ruffle its surface, no mist spread across it, no doubtful movement be in it, no passing cloud darken it, but it must lie still, deep, and transparent... As the sea, when it thus lies still, deep and transparent... reflects the very height of the heavens in its pure depths, so does the heart, when it is still, deep and transparent, reflect the heavenly sublimity of the Good in its pure depths."
- S. Kierkegaard (from the Upbuilding Discourses)