Foreign key on a logical data model?

Foreign key on a logical data model?

I often get into passionate discussions with data modelers on whether a logical data model (LDM) should contain foreign keys. Those that believe an LDM should not include foreign keys explain foreign keys are relational database constructs and therefore should appear on the physical only. Those that show foreign keys explain that foreign keys often increase model readability as it is easier to see how entities relate to each other, and for other reasons as well. What are your thoughts? Do you show foreign keys on a logical? What are your reasons?