Step 1: Plenty of ash indicates that fires have often burned.
Step 2: Fires suggest the preparation of food.
Step 3: Large-scale cooking suggests hospitality to numerous guests.
Step 4: Repeated hospitality points toward the host’s generosity.
The links reflect recognizable practices in the historical social setting, not an exceptionless physical law. A house full of ash is not automatically generous; the rhetorical context invites that particular inference.