In theoretical cosmology Cosmic Inflation sits at the interface between the known and unknown. The end of inflation is designed to connect up with the Standard Big Bang model (SBB) which is highly successful at describing the current observations. Before inflation lies a poorly understood chaotic world where apparently anything goes, and even the laws of physics are not well understood.
Given that inflation is straddling these two worlds, it is not surprising that many open questions exist. Despite these open questions, inflation does a strikingly good job at addressing simpler questions that once seemed deep and mysterious when all we had was the SBB to work with. In particular, inflation teaches how it is indeed possible for nature to set up the seemingly highly ``unnatural'' initial conditions that are required for the SBB. Furthermore, inflation gives us a set of predictive signatures which lie within scope of realistic tests.
Already the confrontation with current observations is strongly favoring inflation. Upcoming large-scale surveys of the Universe promise that the pace of these confrontations will pick up over the next several years. Thus we should know in the foreseeable future whether we should continue to embrace inflation and build upon its successes or return to the drawing boards for another try.
Acknowledgments
I wish to thank Alex Lewin for comments on this manuscript, and acknowledge support from DOE grant DE-FG03-91ER40674, and UC Davis. Special thanks to the Isaac Newton Institute and the organizers for their hospitality during the this workshop.