To begin with, recall that Kantian deontology is a form of deontology that places absolute moral value in the agent’s intent. Like any ethical theory, you can use this to evaluate actions as either permissible or impermissible. In other words, actions that you’re allowed to do and ones that you aren’t.
For Kantian deontology, an action is permissible if it doesn’t violate the categorical imperative, and impermissible if it does violate the categorical imperative.
You might be asking: what does it mean to violate the categorical imperative? First of all, recall that the categorical imperative is the law that gives us reason to act morally under any circumstance, no matter who you are. Violating the categorical imperative, then, means failing to will or intend this universal law.
It might not be clear how you could find out whether or not your action violates the categorical imperative. After all, how can you tell if what you intended is merely due to your particular desires, or if it comes from universal reason?
To help us get a better grasp on the categorical imperative, Kant expressed or formulated it in different ways.
Kant offers several different formulations of the categorical imperative, but one is the formula of universal law and another is the formula of humanity. Both can be used to test whether or not your reasons for acting in a certain way stick to the categorical imperative. We will look at these in more detail in other tutorials. For now, we can briefly sketch their meanings.
In short, the formulation of universal law says that your action is permissible if the reason for the action is one that everyone could find to be a good reason. The formulation of humanity says your action is permissible as long as you don’t disrespect those things that make us truly human (as opposed to being merely animals), such as our freedom.