It's not accurate to say there's one underlying principle that unites all sects of Hinduism. While there are common threads, the vast diversity of Hinduism makes a singular unifying principle difficult to define. Here's a breakdown:

Common Themes:

* Dharma: The concept of duty and right action, though interpreted differently by various schools.

* Karma and Rebirth: The principle that actions have consequences, leading to a cycle of birth, death, and rebirth.

* Moksha/Liberation: The ultimate goal of escaping the cycle of rebirth and achieving liberation.

* The Vedas: Considered sacred texts, though their interpretation varies.

* Respect for All Life: A general reverence for all living beings, including animals, plants, and even inanimate objects.

Diversity:

* Paths to Moksha: Different schools emphasize different paths, like devotion (bhakti), knowledge (jnana), and action (karma).

* Deities: Numerous deities are worshipped, each with specific roles and attributes, reflecting the diverse beliefs and practices.

* Philosophical Schools: Various philosophical schools like Advaita Vedanta, Vishishtadvaita, and Dvaita offer different interpretations of the nature of reality, the self, and the divine.

Therefore, while there are common themes, it's crucial to understand that Hinduism is not a monolith. Each sect holds its own unique beliefs, practices, and interpretations.

A More Useful Approach:

Instead of searching for a singular unifying principle, it's more accurate to understand Hinduism as a family of traditions bound by a shared set of values and practices, but with significant variations.

This understanding allows for a more respectful and accurate appreciation of the diverse and vibrant landscape of Hinduism.