:The argument is more complex than how you are stating it: 1) As for common use, "Gandhi" alone, without "Mahatma" gets many many more Google hits than "Mahatma Gandhi." 2) There is unanimous encyclopedic precedent for the full name, "Mohandas Karamchand Gandhi, which WP:AT#Common_names itself recommends, 3) There is Wikipedia's own convention of naming all Indian polititcal leaders of Gandhi's era by their full names.  Disregarding 2) and 3) will require exceptional explanations. Book titles are not enough, for example, there are twenty five times as many books with title "Goethe", than with title Johann Wolfgang von Goethe, yet the Wikipedia page on the literary genius continues to be Johann Wolfgang von Goethe.  His forenames are hardly recognizably attached to his last name.  Encyclopedic convention is important.