"Ardor, n. The quality that distinguishes love without knowledge"

Ardor is a quality that is frequently associated with love. It is a passionate and intense emotion that is felt with no knowledge or understanding of the things of one's affections. It is a sensation that is often referred to as being frustrating and all-consuming. It is an effective emotion that can be both favorable and unfavorable, depending upon the circumstances.

In this quote, Ambrose Bierce is highlighting the difference between love with understanding and love without understanding. He is suggesting that love without knowledge is identified by ardor, an extreme feeling that is felt without any understanding of the item of one's love. This kind of love is often seen as being more enthusiastic and extreme than love with understanding, as it is not tempered by comprehending or factor. It is an effective emotion that can be both favorable and negative, depending on the circumstances.