Rationale

7 clues
Basis
Grounds
Explanation
Thinking ___
Justification
Underlying reason
Whys and wherefores
Similar answers:
Aaarating
Aberration
Aberrations
Abjuration
Acceleration
Acmecorporation
Adjurations
Administration
Admiration
Adoration
Adorationoftheshepherds
Adumbration
Aerating
Aeration
Afteratime
Agglomeration
Alienimmigration
Alliteration
Alliterative
Alteration