David does not begin with a doctrine but with a relationship: The Lord is my shepherd. Not a shepherd, or the shepherd, but my shepherd — personal, present, responsible for one small, wandering life. And the conclusion he draws is startling in its confidence: I shall not want.
To say we shall not want is not to say we will never feel need. It is to say that the One leading us can be trusted with the need. Sheep are not known for their competence or their sense of direction; their safety depends entirely on the character of the one who leads them. That is precisely the point. Our security was never meant to rest on our own strength.
Today, the same Shepherd who knows the green pastures also knows the valley — and promises to walk us through it, not around it.