The private interest of the individual would not be sufficiently provided for by reasonable and cool self-love alone; therefore the appetites and passions are placed within as a guard and further security, without which it would not be taken due care of.

In this quote, Joseph Butler is discussing the complex nature of human self-interest and how individuals are motivated to care for their own wellbeing. He suggests that self-love, or the desire to take care of oneself, isn't enough on its own to ensure a person's needs are met. Instead, human appetites and passions, which include emotions like hunger, desire, and ambition, play a critical role in driving behavior. These internal forces act as a guard or mechanism, ensuring that people take proper care of their physical and emotional needs.

Butler’s statement underscores a key element of human nature: that people are not purely rational beings. While reason and self-love might encourage a person to care for themselves, it is the passions and appetites that give individuals the necessary drive and urgency to meet their basic needs and pursue their desires. These inner forces add a layer of security to ensure that a person’s self-interest is not neglected or ignored, especially in a world full of distractions and challenges.

Furthermore, Butler implies that the presence of these passions and appetites is not a flaw but rather a crucial part of human design. Without them, individuals might be less motivated to act in their own best interest, potentially neglecting their physical, emotional, and social needs. Therefore, these passions serve a functional purpose in maintaining a person’s wellbeing, acting as a protective mechanism that ensures individuals take the necessary actions to care for themselves.

Ultimately, the quote reflects Butler's philosophical view on human nature, where the balance between reason and passion is necessary to ensure that people adequately care for themselves. The passions and appetites are not merely weaknesses or irrational forces, but rather essential elements that drive human behavior and protect individual wellbeing.