From what I can gather from the stuff I just found, it was released as a single in 1970 but never on an LP until it showed up on various greatest hits collections.
Here's a link to a listing of his albums, but "What is Truth" never shows up on any:
http://www.geocities.com/Nashville/O...9/jcdisc1.html
Here's a link to a listing of his singles where the "What is Truth" single is listed:
http://www.geocities.com/Nashville/O...9/jcdisc2.html
Details on the 45 single:
1970 - COL 4-45134 (CBS 4974) -- What Is Truth / Sing a Travelling Song
Debuted on Billboard on 04/11/70. Peaked at #19
Searching by song title on Amazon and allmusic only brings up various greatest hits/best of collections.