Investigation into the True Teaching by Jens W. Borgland is a translation of the 10th century Jain philosophical Sanskrit text Satyasasanapariksa, composed by Vidyanandin. The text, which is incomplete, presents and refutes 12 Indian philosophical systems, the most important of which are Sautrantika and Yogacara Buddhism, Advaita Vedanta, Nyaya-Vaisesika, Samkhya, Mimamsa and Carvaka. Criticizing these from the standpoint of the Jain anekantavada (theory of manysidedness), Vidyanandin aims to establish the superior status of Jain philosophy. In addition to providing an English translation of this text from the Sanskrit, with explanatory notes, the study places it in the context of Jain philosophy and investigates the arguments Vidyanandin employs in his refutations of his rivals. The doctrines Vidyanandin ascribes to his rivals are also examined and compared to presentations of their doctrines in secondary literature on Indian philosophy and in some cases to how these doctrines are presented in the original literature of the schools in question. Some issues are highlighted as requiring further research. Furthermore the investigation shows considerable influence from Vidyanandin's predecessors Samantabhadra and Akalanka on Vidyanandin's argumentation. The clearest example of this influence is shown on comparing the sections of the Satyasasanapariksa in which Vidyanandin quotes the Aptamimamsa of Samantabhadra (ca 600 CE) with Akalanka's (ca 770 CE) commentary to these verses in his Astasati.