No distortions, e.g. taxes. All utility can be measured in pecuniary terms. No measurement problems. No economics of scale and scope. Time is static or only the dynamic SS is considered.
Human capital can be sold e.g. slavery is legal.
No crime or war and litigation is costless. All property is privately held. All assets are priced and traded in markets. Externalities and exchange may be involuntary. Specificity of investment in production.