Weigh or measure both sugars into a bowl and set them aside. In a separate bowl, weigh or measure the flour, then add the baking soda, baking powder, salt, cinnamon, nutmeg, and allspice. Whisk to combine the dry ingredients.
To plump your raisins, bring water to a boil on the stove or in the microwave. Place the raisins in a bowl and pour enough hot water over them to cover. Let them soak for 10 to 15 minutes, then drain them well before adding them to the cookie dough.
Using a mixer, cream the butter on medium speed for about 1 minute. Add both sugars and continue mixing on medium speed for 3 to 4 minutes, until the mixture is light and fluffy. Add the eggs and vanilla extract, mixing until fully incorporated. Scrape down the sides of the bowl, then reduce the mixer speed to low.
Add the flour mixture to the wet ingredients about one-third at a time, mixing until just incorporated after each addition. Scrape down the sides of the bowl, then add the oats and raisins. Mix on low speed for 10 to 15 seconds, just until combined. If needed, use a spatula to finish folding the oats and raisins into the dough. Chill the cookie dough for 30 minutes.
Preheat the oven to 350°F (175°C or 180°C). Line two cookie sheet pans with parchment paper. Using a medium cookie scoop, place 12 mounds of dough onto each prepared baking sheet. Bake for 12 to 14 minutes, or until the edges are just beginning to turn golden. Be careful not to overbake. These cookies can become hard after a few days if baked too long.
Once you remove the cookies from the oven, the tops will still feel soft but will firm up as they cool. Let the cookies rest on the baking sheet for 1 to 2 minutes, then transfer them to a wire rack to cool completely.