He was a scholar in his native Malayalam, as well as in Sanskrit and Tamil, and also mastered English, Hindi, Telugu, Kannada, Greek, Latin, Hebrew, and Syriac.
In the 1920s, he took on Krishan Namboodri (who later became known as Swami Agamanda), Rishiram, and R. C. Das, who were promoting Hindutva and opposing conversion.
Some of his books covered areas of Christian apologetics such as Prathiyukthi, and Satyaprakashini and Krushil Maricha Kristhu (Christ who died on the Cross), — which were compiled from notes prepared from his rebuttals to anti-Christian critics.
Simon also spoke out against Russian traveller Nicolas Notovitch's controversial claims that Jesus had visited India between the ages of twelve and thirty, studying under Hindu, Buddhist, and Jain teachers.
In Krushil Maricha Kristhu (Christ who died on the Cross), Simon cited research by German scholar Max Muller, which he said exposed Notovitch's claims as a hoax.
It is a literary classic, and it earned him the title of Mahakavi (Dean of Poets), conferred on him by the Sahitya Parishad (Academy of Literature).