Step 1: Buddhist philosophical schools.
Buddhism encompasses several schools/traditions that present various philosophical viewpoints. The prominent ones include Sautrāntika, Vaibhāṣika, Yogācāra, and Mādhymika.
Step 2: Sautrāntika.
The Sautrāntika school considered only the Sūtras as authoritative and separately accepted the Abhidharma texts. This is a Buddhist tradition.
Step 3: Vaibhāṣika.
The Vaibhāṣika school emphasized the Abhidharma and wrote extensively on dharma-vibhāga. This is also a Buddhist tradition.
Step 4: Mādhymika.
The Mādhymika school, attributed to Nāgārjuna, is known for Śūnyavāda. It is a doctrine of the Mahāyāna tradition.
Step 5: Sāṁkhya.
Sāṁkhya is a Hindu philosophy with a dualistic system of Puruṣa and Prakṛti. It is not part of the Buddhist tradition.
Step 6: Conclusion.
The correct answer to this question is Sāṁkhya.