Identical paths in different databases can't be serialized

[Bosdongen]

When I use this configuration in unicorn this an error is thrown.

<predicate type="Unicorn.Predicates.SerializationPresetPredicate, Unicorn" singleInstance="true">
   <include database="core" path="/sitecore/system/Settings" />
   <include database="master" path="/sitecore/system/Settings" />
</predicate>

Throws this error

Multiple predicate include nodes had the same name 'Settings'. This is not allowed. Note that this can occur if you did not specify the name attribute and two include entries end in an item with the same name. Use the name attribute on the include tag to give a unique name.

[kamsar]

From the error message:

"Note that this can occur if you did not specify the name attribute and two include entries end in an item with the same name. Use the name attribute on the include tag to give a unique name."

If no name is specified, the include name becomes the last segment in the path - in this case Settings.

You should make one, or both, of the includes something like <include name="Core Settings" database="core" path="/sitecore/system/Settings" />