It seems inevitable to me that life has a purpose, for if it had none, if our lives were meaningless, then we should have no reason to want meaning, for we could not even discern the absence of meaning. Discounting outliers, we all know instinctually that there is a right and a wrong, and this is only another way of saying that there is an ultimate end that something can be working for or against. That end, in the end, is ultimately your God whether you choose to name it as such.