Step 1: Introduction to Buddhist Logic.
Buddhist logic, or Hetuvidyā, saw significant development through the contributions of scholars such as Dignāga and Dharmakīrti.
Step 2: Dharmakīrti's Significance.
Dharmakīrti, active in the 7th century CE, is recognized as a preeminent Buddhist logician who advanced the fields of epistemology and logic.
Step 3: Evaluation of Candidates.
- Buddhaghoṣa: Primarily known as a commentator, not a logician.
- Aśvaghoṣa: Celebrated poet and playwright, credited with the Buddhacarita.
- Dharmakīrti: Identified as the key Buddhist logician.
- Vasubandhu: A philosopher, though not primarily recognized for his contributions to logic.
Step 4: Final Determination.
Therefore, the identified Buddhist logician is Dharmakīrti.