Don't even look for a path
Outside of crime and sin, what else does the straight and narrow involve?
It implies that a virtuous life is one that is strictly restricted to a single course, and a single goal. It implies that you shouldn't so much as look at the landscape as you go by for fear of curiosity leading you off the path. It implies that life is about having a goal, and working tirelessly, steadily, towards it.
I'll tell you, in case you haven't already worked it out for yourself, what lies at the end of the road of life:
Whichever way you look at it, and whatever you may believe about what does, or does not, come after, death is the point that you can't see past.
The injunction to stay on the path means something else, as well, therefore. It means "do as you are told"; "don't think for yourself"; "don't think outside the box"; "don't try to change what you are"; "don't try to learn for yourself".
By sticking to the straight and narrow you accept your lot in life, as defined by others. You permit yourself to be channelled into blinkered conformity, and because you only go forward (for fear of being left behind, quite often) and keep your eyes on that distant goal that all to soon you recognize as the end of the road, you never discover your own potential.
If you leave the path, you soon discover that you have a whole lot to learn. Off the path, there is so much to learn that noone even knows 1 millionth of 1 millionth of it. And the experience of two different people off the path can be so different that their views seldom coincide. But get this: there isn't only one straight and narrow. Different societies, tribes, religions, at different times and in different places define different ruts, but since all those paths lead from the same place to the same place (birth to death, if you like), those paths are all parallel. They never coincide at all.
How surprising is it that the differences between fundamentalist Moslims and fundamentalist Christians are irreconcilable. The key word is fundamentalist. Fundies always insist on the straight and narrow - they know that a little knowledge from off the path is all you need to discover freedom.
For me, what this is all about is two things: freedom and individuality. The straight and narrow is often defended by the "ideal" of equality. But I'm opposed to equality wherever it doesn't promote freedom. Gender equality is a perfect example of this. There are differences between all men and all women. I know this especially well as a man raised to try to think like a woman. The differences mean that equality is as meaningless as competition. Gender freedom is defined as the removal of all obstacles to self determination that are imposed on the grounds of gender. It's a kind of "right to try". My maternal grandfather believed that women should not even try to drive a car. That is restricting gender freedom. Gender freedom is ensuring that men and women can try to do the same things, without restriction or prejudice, and that each individual be judged (if need be) on the results.
If there is a current world financial crisis, if there is a population crisis, if there is an environmental crisis — I say "if" because there's always some sort of problem to overcome, and it really doesn't matter if these current media-sexy threats are true or not (though there are compelling reasons to think so) — then they will not be solved by conformity. Straight and narrow thinking has lead to all three. Off the path thinking will solve them.
When you go off the path, you discover, you learn, and you become different. Many people fear those who are different (most people fear those who are incomprehensible), and many people fear becoming different. This is understandable, but harmful. There are people in the world who are pursuing a dream of anti-gravity that uses gyroscopes and perpetual motion. There are people pursuing room-temperature (cold) fusion. They may be incomprehensible and uncomprehending crackpots, but they are off the path; they may not be expanding human knowledge, but they are broadening our culture. Culture needs breadth, if we are to survive. We need our crackpots and charlatans. We need our poets, artists and mystics. We need our free thinkers and yes, we need our lunatics. Whether they like it or not, they are exploring the extremes of what it means to be human.