In override equal method, this keyword is not pass as a parameter while comparing the attributes?

Question

I have seen lots of example of overriding equals method. But in every example, while fields comparison, why we don't pass parameter like this.firstName in Objects.equals(firstName, person.firstName), but just pass firstName

Why we don't write like Objects.equals(this.firstName, person.firstName)

public boolean equals(Object o) {
    // self check
    if (this == o)
        return true;
    // null check
    if (o == null)
        return false;
    // type check and cast
    if (getClass() != o.getClass())
        return false;
    Person person = (Person) o;
    // field comparison
    return Objects.equals(firstName, person.firstName)
            && Objects.equals(lastName, person.lastName);
}