Berkeley's 'esse is percipi' has been criticized for implying epistemological solipsism, the main argument being that different minds cannot harbor numerically one and the same idea. Similarly, C. J. Boström, the dominating Swedish philosopher in the 19th century, was early scorned because his principle of esse est percipi allegedly contradicts the simultaneous claim that two spirits (God and a human, or two humans) can perceive the same thing under qualitatively different appearances. Whereas the criticism against Berkeley is here regarded as valid, it is argued that Boström successfully defended himself by employing a dual concept of meaning, resembling Frege's Sinn and Bedeutung some thirty years later, and by postulating an ontology that permits human minds to share in the divine ideas that constitute reality.