In English
The objection may be raised that words like sky-flowers or castles-in-the-air do not denote any concrete tangible reality. But these are not words, they are compounds, artificial strings of words. Consider another example of Form and No-form. Take this pillow. You described it as cotton enclosed in a cloth bag. I disclose that the cloth too is cotton. The shapeless, formless cotton has become yarn and by dealing with the yarn as warp and wool the cloth has put in form for the bag and the pillow.