Indian Philosophers

Step 1: Identify Arya Samaj.
Arya Samaj was a socio-religious reform movement in India, founded in 1875. Its aim was to reform Hindu society and return to the teachings of the Vedas.

Step 2: Founder.
Swami Dayanand Saraswati, a reformer and religious leader, established Arya Samaj in Bombay (now Mumbai).

Step 3: Distinguish from others.
\begin{itemize} \item Raja Rammohan Roy founded the Brahmo Samaj. \item Swami Vivekananda founded the Ramakrishna Mission. \item Mahatma Gandhi led the freedom struggle but was not connected with Arya Samaj. \end{itemize}

Step 4: Conclusion.
Hence, the correct founder is Swami Dayanand Saraswati.

Final Answer: