904. The spiritual have their own proper felicities, and these are distinguished from the celestial by means of the gladness that the spiritual have and the joy the celestial have. In order that states of gladness or spiritual felicity may be understood, an idea of them can be gained from the harmonies of sounds; also from the harmonies of visual things. The harmonies of sounds, also those of speech, besides the meaning of speech, pertain to spiritual harmony. The gladness which thence results is a spiritual gladness; therefore the music of the Church of old was so delightful, as also the singing in the heavens. So likewise the harmony of visual things; hence are the varieties of beauty which affect the mind, such as beauty in general, as also the beauty of paradises and of all similar things, and that of buildings. These pertain to spiritual gladness. Then, more interior gladness is the gladness in intellectual things; hence is the love of truth itself, or of truths, consequently also of cognitions. States of spiritual gladness are the forms of celestial things which are their essentials; if they are not, they still should be.