Some theories about the positive impact of markets on morality suggest that competition increases empathy, not between competitors, but between them and third parties. However, empathy may be a necessary evolutionary antecedent to guile, which is when someone knows what the other person wants and intentionally deceives him or her, and deception may have evolved as a means of exploiting empathy. This paper examines how individuals primed for empathy behave towards third parties in a simple economic game of deception. It reports the results of a data entry experiment in an online labor market. Individuals enter data randomized to be a prime for empathy, for guile, or a control. Empathy is then measured using a Reading the Mind in the Eyes Test and guile is measured using a simple economic game. Individuals primed for empathy become less deceptive towards third parties. Individuals primed for guile become less likely to perceive that deceiving an individual is unfair in a vignette. These results are robust to a variety of controls and to restricting to workers who entered the prime accurately. These findings are inconsistent with the hypothesis that empathy causes guile and suggests that empathy may cause those who are making judgements to become less deceptive.