I wonder if the idea of "believing in" Jesus is confusing to some non-Christians. In non-religious usage, to "believe in" something or someone means "to have confidence/trust in" or just "to think that something exists".
"Believing in Jesus" is often defined in terms of a relationship of trust for salvation. It seems to me that that emphasis, without more explanation, could make it easy to forget the part about actually believing Him (i.e., that what He taught is true). It could perhaps also leave one open to a bait-and-switch accusation once you tell a person that they need to actually do certain things (e.g., obey Jesus).
In John 3:12, Jesus asks, "If I told you earthly things and you do not believe, how will you believe if I tell you heavenly things?" Then in verses 15 & 16, he says, "... everyone who believes in [en] Him ...," and "... everyone who believes in [eis] Him ...." It seems that other prepositions are used in other verses (1 Timothy 1:16), which are sometimes translated as "on" rather than "in". I guess that the different Greek prepositions all have more or less the same meaning, but maybe not?
Jesus also spoke about those who "believe in all that the prophets have spoken." I haven't had a chance to look at other uses of "believe in/on" in the NT.
Mattrose's John 3:16 Believes chapter is good and helpful, and I've googled these things a bit. But I'd like to read any thoughts you all have about any of this, if any. It may very well be a much too narrow and unnecessary focus.
Thanks.
