This is a usage specific to the religion of "Christian Science", a religion basically created by Mary Baker Eddy in 1870s.
Christian Science defines the Trinity as Life, Truth, and Love, which are three of the seven synonyms that Mrs. Eddy uses to describe God. (The seven synonyms are Principle, Soul, Mind, Spirit, Life, Truth, and Love.) [http://www.christianway.org/CS%20and%20the%20Bible/trinity.htm]The seven synonyms are Principle, Soul, Mind, Spirit, Life, Truth, and Love.
Christians, Jews, and others often capitalize any noun or pronoun use to refer to God. So you don't write, "God did this ... then he did that"; you write "then He did that". Or you might refer to God as the "Creator" rather than the "creator", etc. Miss Eddy decided that these 7 words were names or descriptions of God, and so she capitalized them when used in that context.
I suppose Christians might also capitalize these words if they used them to refer to God, like a Christian might write, "God is Truth" rather than "God is truth". But mainstream Christians do not see these 7 words as having any special significance like Christian Scientists do, that is, no more significance than any other word you might use to describe God.