For man two wings are necessary. One wing is physical power
and material civilisation; the other is spiritual power and divine civilisation.
With one wing only, flight is impossible. Two wings are essential. Therefore,
no matter how much material civilisation advances, it cannot attain to
perfection except through the uplift of spiritual civilisation.
- 'Abdu'l-Bahá (‘Promulgation of Universal Peace’; The Compilation of Compilations, Vol.III,
Social and Economic Development)
