The Tattvacintamani, or Jewel of Reflection on the Truth (about Epistemology), is the sole composition left us by the great fourteenth century Indian logician Gangesa Upadhyaya. With this foundational text Gangesa solidified the "New" (navya) phase of the long-running school of epistemology and metaphysics known in India as Nyaya. The present work is a translation of the perception chapter (Pratyaksa-khanda) of this important text. The authors have provided an introduction covering essential theoretical and historical background, and a comparison of Nyaya with Western epistemological traditions. The translation is augmented with a detailed running commentary which presents further background, contextualization, analysis, and comparison. Includes a glossary explaining in English every Sanskrit word used, brief characterizations of persons and schools, and a detailed Index.