अग्निशिखाः Means flame of fire. This "Nyaya" has been conceptualized on the flame of fire.
Naturally the flame of fire always goes up. If a burning log of wood is pointed upward or downward, its flame will always move upwards. Thus it is the nature of the flame of fire to move upward, it never moves downward.
In the similar manner, a person should make his nature stable, such as nature of benevolence. If a person cultivates the nature of benevolence, then he always remains benevolent towards others. He remains engaged in benevolent activities whether the situation is favorable for him or not or whether there is convenience of time or recourses or not. In the similar manner, if a student makes his nature to acquire knowledge, then he will always remain engaged in the activity of acquiring knowledge whether he has extra time or not, whether circumstances in his family are favorable or not. The essence is this that a person must cultivate his nature and maintain it as the flame of fire.
Thus, this 'Nyaya' explains that a person should always try to keep up his noble nature.