Depending on what part of speech it is, the term may also be translated as "truly sincere," "truly," or "sincerely."
This article focuses mainly on four aspects of the scriptural use of the term.
First, "sincerity," which is generally taken to mean freedom from pretence or deceit, denotes the stance of mind that is in accordance with what is true or real. Tenrikyo's Scriptures--which also describe sincerity as being in perfect accord with the "truth of heaven"--contain such passages as the following:
But if you are truly sincere, I shall teach you everything whatever.
Ofudesaki XIV: 80
If your mind is truly sincere, there will never be a failure in any salvation.
Ofudesaki XIII: 71
No matter how hard one may try to destroy the one truth of true sincerity, it can never be done.
Osashizu, May 26, 1890
Second, the word "true" in the phrase "true sincerity" can be seen as adding emphasis to sincerity.
This fertilizer: do not wonder what is effective. The mind's true sincerity is its effectiveness.
Ofudesaki IV: 51
You wonder why you get bodily disorders after you have shown so much devotion. It is such thoughts--which you entertain in the course of daily life--that cause the bodily disorders. If true sincerity is established in you, the bodily conditions will clear up quickly.
Osashizu, June 18, 1889
Replace your mind even in the span of a night! Settle the mind in true sincerity and set aside three days for the attempt. If you settle the mind firmly, you will see [the truth] clearly.
Osashizu, around September 1888, supp.vol.
Third, among the Divine Directions through which the truth of the Sazuke was bestowed, there are some that connect sincerity with the heart. This may be related to the fact that Yoboku, who have received the truth of the Sazuke, are taught that "the mind of saving others is the real truth of sincerity alone." Sincerity's connection with the heart is found in such passages as the following:
With each of you, the constancy of true sincerity allows for free and unlimited workings. Do not wonder where free and unlimited workings are. With each of you, the mind called the heart's sincerity is where the free and unlimited workings are. Sincerity is the truth of heaven. Also, the truth of the mind that allows for harmony in the family is the truth of heaven. I accept it at once and give a return at once.
Osashizu, December 25, 1888
Fourth, the adverbial use of the term in question may sometimes be seen as giving emphasis to what follows it and imparting the quality of true sincerity to the action described (underline added in the following extract to highlight the term).
Though you are saying that this world is the world of God, you do not know the core of all matters.
I shall truly manifest this core. When you see it, be convinced, all of you.
Other examples include Ofudesaki X:22-23.
An additional facet of the use of this term is found in The Doctrine of Tenrikyo, which stresses true sincerity as a quality in one's mind that could be seen as a supreme virtue. We read:
When the mind of tanno [joyous acceptance] is settled and the body is spirited through efforts of hinokishin in which greed is forgotten, there will emerge the virtue of true sincerity, a virtue which is most acceptable to God the Parent. Then our lives will overflow with clearness and brightness. We shall be able to perceive the intent of God the Parent without error and respond in exact manner.
The Doctrine of Tenrikyo, p. 62(This article was first published in the June 2007 issue of TENRIKYO.)