Which of the following Buddhist text dealt with philosophical matters?

Abhidhamma Pitaka

Interestingly, none of the Buddha's speeches were written down during his lifetime. However, after his passing in the fifth or fourth century BCE, his disciples compiled his teachings during a council of "elders" or senior monks at Vesali (present-day Vaishali, Bihar). These compilations were collectively known as the Tipitaka, signifying three baskets that contained different types of texts. Initially transmitted orally, they were later written down and classified based on their length and subject matter.

The Tipitaka consisted of the Vinaya Pitaka, which included rules and regulations for those who joined the monastic order (sangha); the Sutta Pitaka, containing the Buddha's teachings; and the Abhidhamma Pitaka, which delved into philosophical matters. Each pitaka comprised multiple individual texts. Over time, Buddhist scholars wrote commentaries on these texts.