Like Benjamin Spock before them, William and Martha Sears consider their parenting philosophy as a common sense and instinct-guided ad hoc way of parenting.[88] In contrast to Spock who derived his ideas in a straight line from Freud’s psychoanalysis, the Sears in fact didn’t start out from a theory; even the tie to attachment theory was only engineered ex post, when the philosophy was already largely complete. Apart from Liedloff’s rather eclectic thoughts, they came to their ideas mainly from their own personal impressions:[89]