Robin May, Gresham Professor of Physic and Professor of Infectious Disease at the University of Birmingham, asks whether emotional states should be deliberately altered now that neuroscience is making it increasingly possible. He starts with manipulation we already accept, from Lyndon Johnson's use of physical proximity to persuade colleagues to the proven effect of ambient smells on mood, before weighing the ethics against cases like hate crime prevention versus dictatorial control. The lecture surveys how mood stabilizers such as lithium, SSRIs, MDMA and psilocybin work on the brain, including promising trials of psilocybin for PTSD and the military's interest in psychoactive drugs. May then turns to non-human manipulators of emotion and behavior: the cordyceps fungus that controls ants, rabies' effect on serotonin, and Toxoplasma gondii, a parasite carried by roughly a third of people. He closes on brain-computer interfaces, Neuralink, and the gut microbiome's influence on personality, asking how much of a person's emotional life is really their own.