Yes: If you don’t know where you’re going, how can you chart a course to get there?
A whole lot can happen in the middle, some of which might take you by surprise and affect the ending, but when you pull out your star charts, and man the ship’s wheel all night, closing the distance between you and your destination is the point. No destination, and you might just sail around in circles.
Think through your story, to know where it begins and how it will proceed to a satisfying and believable conclusion.
If you discover that the story doesn’t hold up, or a character isn’t working, or that the ending is all wrong, you will have to step back, throw out what isn’t working, and plan your story anew.
This sense of change, of flux, of being available to your talents and instincts even when they require that you set a new course, has sometimes been described as the story writing itself.
So yes, you absolutely need to know your ending and aim for it if you expect to get there . . .
But: a secure writer, trusting in his process, will move with his story, instead of against it.
Comments welcome and edited to include first names only, and website, if provided; never your email. Photo credits: ship’s wheel by Stephen Glenn; stars by howardedin.com