Abdul-Bahá said:
It is a lovely day, the sun shines brightly upon the earth, giving light and warmth to all creatures. The Sun of Truth is also shining, giving light and warmth to the souls of men. The sun is the life-giver to the physical bodies of all creatures upon earth; without its warmth their growth would be stunted, their development would be arrested, they would decay and die. Even so do the souls of men need the Sun of Truth to shed its rays upon their souls, to develop them, to educate and encourage them. As the sun is to the body of a man so is the Sun of Truth to his soul.
A man may have attained to a high degree of material progress, but without the light of truth his soul is stunted and starved. Another man may have no material gifts, may be at the bottom of the social ladder, but, having received the warmth of the Sun of Truth his soul is great and his spiritual understanding is enlightened.
A Greek philosopher living in the days of the youth of Christianity, being full of the Christian element, though not a professing Christian, wrote thus: It is my belief that religion is the very foundation of true civilization. For, unless the moral character of a nation is educated, as well as its brain and its talents, civilization has no sure basis.
As religion inculcates morality, it is therefore the truest philosophy, and on it is built the only lasting civilization. As an example of this, he points out the Christians of the time whose morality was on a very high level. The belief of this philosopher conforms to the truth, for the civilization of Christianity was the best and most enlightened in the world. The Christian Teaching was illumined by the Divine Sun of Truth, therefore its followers were taught to love all men as brothers to fear nothing, not even death! To love their neighbours as themselves, and to forget their own selfish interests in striving for the greater good of humanity. The grand aim of the religion of Christ was to draw the hearts of all men nearer to Gods effulgent Truth.
~ From "Paris Talks"