"Whoever marries the spirit of this age will find himself a widower in the next"

This quote by William Ralph Inge is a warning against following the trends of the present age. It suggests that if somebody follows the spirit of the age, they will be left in the next age. Inge is cautioning versus blindly following the trends of the current age, as they will not last. He is recommending that it is much better to be independent and think for oneself, rather than merely following the crowd. Inge is alerting that if somebody follows the spirit of the age, they will be left in the next age, and will be a "widower" in the sense that they will be alone and without the support of the present age. Inge is recommending that it is better to be independent and think for oneself, instead of simply following the crowd. This quote is a reminder to believe for oneself and not be swayed by the trends of the existing age, as they will not last.