Among the most promising options for vindicating Oppenheim and Putnam’s unity of science hypothesis is the ‘Mentaculus’ of Albert and Loewer. I assess whether this promise can be borne out. My focus is on whether the Mentaculus can deliver what Oppenheim and Putnam call the ‘unity of laws’: the reduction of special science laws to the laws of fundamental physics. I conclude that although the Mentaculus may support a fairly strong form of reductionism, it falls short of upholding the unity of laws.