In Act II, Scene 2 of Hamlet, Rosencrantz and Guildenstern disagree with Hamlet when the prince states that Denmark is a prison. In response, Hamlet responds, “There is nothing either good or bad, but thinking makes it so.” This line is an appropriate foundation for a review of Fathali M. Moghaddam's Shakespeare and the Experimental Psychologist (2021).A review is merely one person's opinion, a fact that I am conscious of as a theater critic with 15 years of experience reviewing live stage productions, ranging from amateur plays to Broadway and international shows. Readers should hope that a review is an informed opinion from a person with a broad knowledge base in the relevant topic. But it is still an opinion. Therefore, readers should examine Moghaddam's book for themselves to decide whether my viewpoint is justified. When passing judgment on an artistic or scholarly work, there really is nothing either good or bad, but its audience's thinking makes it so.But in my other identity as a psychological scientist, I adhere to the viewpoint that there is an objective reality worth studying and that scientific methods are equipped to uncover truth about that reality. From this perspective, thinking does not make it so; objective reality exists, regardless of what (or whether) humans may think about it. Denmark is not really a prison for Hamlet, and his belief that it is does not make it one.Moghaddam's principal thesis in Shakespeare and the Experimental Psychologist is that “Shakespeare himself was an experimentalist” (p. ix) and that Shakespeare wrote several thought experiments into his plays that shed light on human behavior. It is an intriguing thesis that is worth examining. However, the evidence falls short.One problem is that Moghaddam does not define a thought experiment carefully enough for there to be a clear boundary between which events in Shakespeare's corpus qualify and which do not. Thus, for Moghaddam, Macbeth is a thought experiment about the influence of an external psychological “scaffolding” on the title character's behavior. But it is never clear why Romeo and Juliet is not a thought experiment on the influence of context on young people's behaviors. Why is The Tempest a thought experiment showing how a change in environment—a shipwreck—can result in a change in behavior, but The Comedy of Errors or Twelfth Night (plays also starting with a shipwreck) is not? Moghaddam never explains.A second problem is that Moghaddam treats Shakespeare's writings as being equivalent to actual observation of real humans’ behavior. But they are not. His characters are either fictional or (in the history plays) heavily fictionalized. Works of fiction, at best, provide evidence about the author's beliefs about human behavior; they are not records of behavior itself. If an author's assumptions and beliefs about human nature and the physical world are incorrect, then a work of fiction will produce inaccurate, distorted, or completely false “data.”In fact, Moghaddam sometimes seems to ignore the fictional nature of Shakespeare's characters, and he treats them as behaving the way real humans do. In Moghaddam's view, Othello's jealousy does not become a flaw until Iago manipulates the Moor of Venice. Anne's decision to marry Richard III occurs “very surprisingly” (Moghaddam, 2021, p. 15), and Macbeth does not begin his murderous behavior until the character's context changes. But all of this ignores the fact that Shakespeare could have written something else and made these characters behave in other ways. Indeed, in the earliest recorded version of the story, Hamlet travels to England, marries the daughter of the English king, and returns to burn the Danish king's hall down, killing the usurper and his men who are trapped inside (Hansen, 2000). Neither version of the Hamlet legend tells readers anything objective about human behavior because an author could just as easily tell a version in which the prince acts differently.Even if one accepts Moghaddam's premises, his conclusions are often based on shaky psychological science. Moghaddam cites Zimbardo's Stanford Prison Experiment (SPE) and the research on embodied cognition as supporting his views, even though the SPE has been thoroughly undermined, possibly discredited (Le Texier, 2019), and much of the research on embodied cognition does not replicate (e.g., Lynott et al., 2014; Wagenmakers et al., 2016). Moghaddam also denies the existence of enduring personality traits, going so far as to claim that “individuals do not have fixed personalities” (Moghaddam, 2021, p. 169). Instead, he believes that personality, such as it is, emerges solely from the environmental context. Macbeth is engaged in villainy not because evil lurks within his soul but because the witches and Lady Macbeth create the circumstances wherein evil can occur. With environment having supreme importance, Moghaddam's interpretations of Shakespeare's work reflect a blank slate view of psychology, contrary to the overwhelming evidence from behavioral genetics and evolutionary psychology (see Pinker, 2003, and Plomin, DeFries, Knopik, & Neiderhiser, 2016, for accessible summaries of these fields’ findings).From a literary perspective, Moghaddam sometimes even grossly misreads the messages of Shakespeare's plays. For example, he claims that “Shakespeare also helped to cultivate the roots of modern democratic movements” (Moghaddam, 2021, p. 191). In reality, Shakespeare distrusted democratic rule and saw it no differently than mob rule. In Julius Caesar, the masses are portrayed as fickle, easily manipulated (Act I, Scene 2; Act III, Scene 2), and even dangerous (Act III, Scene 3; see also Henry VI, Part 2, Act IV, Scene 2). Shakespeare's ideal government is a strong absolute monarchy, ruled by a moral king who wields unquestioned power and whose main duty is to establish societal order. Henry V is the clearest example, but the importance of a moral ruler appears often in Shakespeare's work, even in minor characters, such as Fortinbras in Hamlet or the prince in Romeo and Juliet.A reader of Shakespeare and the Experimental Psychologist will actually learn little about Shakespeare or psychology. The book reveals far more about its author (e.g., his concern about authoritarianism, his enthusiasm for social psychology) than about either of its putative topics. Moghaddam's ideas are intriguing, but they are not sufficiently supported by empirical psychological research or Shakespeare's text to be useful. In this case, thinking does not make it so.