[1] Born in Mojowarno, East Java, in 1869, Kruyt grew up in a missionary family[2] and went to the Netherlands for education in 1877.

The Nederlandsch Zendelinggenootschap (NZG, Netherlands Missionary Society) sent him to establish a new mission in Poso in 1892.

Kruyt is known for his ethno-sociological approach, believing that understanding local cultures was essential for successful missionary work.

[8] He argued that missionaries must understand the link between thought and community life to win hearts[9] and preferred voluntary conversions over coercion.

[6] His works on ethnography and evangelism are highly valued, especially the book he co-authored with Nicolaus Adriani, De Bare'e-sprekende Toradja's van Midden-Celebes (The Bare'e speaking Toraja of Central Sulawesi), which remains a key ethnological resource.