This article explores Robert E. Lucas's policy agenda and his engagement with the public debate between 1968 and 1987. It investigates how he interacted with the public debate by envisioning key principles of his macroeconomic theory and methodology, and how he promoted his policy agenda. An exploration of Lucas's personal and professional archives sheds light on his participation on policy debates after the publication of his topical works, illustrating how Lucas developed a unique way of dealing with science in the public debate by building a distinctive, discreet and cautious way of engaging with the public. Lucas did not embody the traditional elements of an "economic expert": he did not envision an action plan, nor proposed a detailed program to successfully implement his policy agenda. The article suggests that, unlike other economic experts, Lucas's participation in the public debate was "unintended": the public always solicited Lucas to express his opinion and advice, not the opposite.JEL Codes: B22, E30, H10