What is the substance of capacity in relation to testamentary dispositions and gifts?

In Slover v. Rellinger, 2019 ONSC 6497, the court commented on the substance of capacity in relation to testamentary dispositions and gifts (citations omitted): 370 To lose testamentary capacity on the basis that the testator lacks a sound and disposing mind, a lack of mental capacity or mental disorder must be established. This is more than being "eccentric, unfair or capricious"... It is more than entertaining "wrong-headed notions" and doing "eccentric ... absurd and foolish acts"... "Such things as imperfect memory, inability to recollect names and even extreme imbecility, to not necessarily deprive a person of testamentary capacity" provided that the testator's mind is sufficiently sound to understand the nature of the property being bequeathed... A will-maker can be unfair, capricious and even mean but still have testamentary capacity so long as the testator does not suffer from a mental disorder… "A testator has the right to treat hopeful beneficiaries unjustly", so long as there is testamentary capacity…