Paul Believed That One Could Believe -- In Vain.

IN VAIN.

Greek = εἰκῇ = without success or effort.

      ·         1 Corinthians 15:2 (ESV)  and by which you are being saved, if you hold fast to the word I preached to you—unless you believed in vain.

      ·         1 Corinthians 15:10 (ESV)  But by the grace of God I am what I am, and his grace toward me was not in vain. On the contrary, I worked harder than any of them, though it was not I, but the grace of God that is with me.

      ·         2 Corinthians 6:1 (ESV) Working together with him, then, we appeal to you not to receive the grace of God in vain.

      ·         Philippians 2:16 (ESV)  holding fast to the word of life, so that in the day of Christ I may be proud that I did not run in vain or labor in vain.

      ·         1 Thessalonians 2:1 (ESV) For you yourselves know, brothers, that our coming to you was not in vain.

      ·         1 Thessalonians 3:5 (ESV) For this reason, when I could bear it no longer, I sent to learn about your faith, for fear that somehow the tempter had tempted you and our labor would be in vain.

It is possible that one can labor in the Gospel and that people can believe – IN VAIN; that is "without purpose or success."  If there is no perseverance; if there is no standing in the face of opposition and persecution – one may have believed in vain!