Put the meaning into your own words.

It would be foolhardy to begin the long hike without a map.

Sal's friend Vic was overconfident about spotting valuable prints after watching a single introductory demonstration. He became gullible when a stranger's unsupported story about a supposedly rare edition persuaded him without any attempt to check it. His proposal to carry a large framed purchase down a visibly unstable staircase was foolhardy despite the available safer route.