All of us, I believe, are fortunate to have been born. - Thomas Nagel

A feature of experience is subjective if it can in principle be understood only from one type of point of view: that of a being like the one having the experience, or at least like it in the relevant modality. The phenomenological qualities of our own experiences are subjective in this way. The physical events in our brains are not. Human physiologists may take a special interest in them; but they can, in principle, be understood just as well, or even better, by creatures totally unlike us in physical and mental structure. To understand them such creatures need not take up our point of view. Physical brain processes can be understood objectively, from the outside, because they are not subjective phenomena. And no description or analysis of the objective nervous system, however complete, will ever by itself imply anything which is not objective, i.e. which can be understood only from one kind of viewpoint, that of the being whose states are being described. One cannot derive a pour soi from an en soi.

I am not adverting here to the alleged privacy of experience to its possessor. The point of view in question is not one accessible only to a single individual. Rather it is a type. It is often possible to take up a point of view other than one's own, so the comprehension of such facts is not limited to one's own case. There is a sense in which phenomenological facts are perfectly objective: one person can know or say of another what the quality of the other's experience is. They are subjective, however, in the sense that even this objective ascription of experience is possible only for someone sufficiently similar to the object of ascription to be able to adopt his point of view — to understand the ascription in the first person as well as in the third, so to speak. The more different from oneself the other experiencer is, the less success one can expect with this enterprise.

[T]he essence of the belief that bats have experience is that there is something that it is like to be a bat. Now we know that most bats (the microchiroptera, to be precise) perceive the external world primarily by sonar, or echolocation. … But bat sonar, though clearly a form of perception, is not similar in its operation to any sense that we possess, and there is no reason to suppose that it is subjectively like anything we can experience or imagine. This appears to create difficulties for the notion of what it is like to be a bat.