User blog comment:IamJakuhoRaikoben/Chapter 464: Natsu vs Zeref, Review./@comment-4933386-20151130223153/@comment-24039234-20151130225942

You can't really test something you have only one shot of, can you?

So it's a gamble Natsu is willing to take, since it is something that comes from Igneel. While I agree that Natsu is not the brightest banana in the bunch, I have no problem accepting his decision, on an emotional basis, at least.