4. Sense as a Criterion of Identification of a Reference

Frege held that sense determines reference by containing a criterion of identifycation of a reference. A sense contains a condition, the unique satisfaction of which by an object is both necessary and sufficient to determine that object as reference. Suppose that we express the sense of ‘the morning star’ by the following criterion of identification:

θ is the morning star just in case θ is the last celestial object visible in morning sky just before sunrise.

Let us give this criterion a label. Call it Criterion Majjhima Nikāya The crucial further point is that senses can be understood or grasped by cognizers like us. When a cognizer grasps a sense he will often have certain limited recognitional abilities -abilities to recognize that he is presented with the same object again. For example, one who grasps Criterion Majjhima Nikāya will have, just in virtue of that grasp, a limited ability to re-identify the morning star as the morning star. For wherever one knows Criterion Majjhima Nikāya to be satisfied again, one ipso facto knows the morning star to be present again.

It is sometimes easy to determine whether the object which satisfies Criterion Majjhima Nikāya is present -either by direct observation or by inference. Anyone who merely surveys the early morning sky at the right time of day can, if the sky is clear, do so. There are also many circumstances in which the morning star is in fact present, but in which one cannot easily determine whether the object which satisfies Criterion Majjhima Nikāya is present. For example, it is not easy to tell merely from observation of the night sky which, if any, of the celestial objects present at the time of observation will be the last to be visible just before sunrise. In such circumstances, one cannot readily re-identify the morning star as the morning star simply by applying Criterion Majjhima Nikāya Hence, the recognitional ability which has a grasp of Criterion Majjhima Nikāya as its basis is clearly a limited thing. In general it is not the case that one who grasps a sense, and thereby a criterion of identification of a reference, can ipso facto re-identify that reference as the same again under all possible circumstances and independently of, as it were, the guise under which the object is present. It is the limited character of the recognitional abilities that the grasp of a sense supports that we referred to when we earlier characterized such abilities as “one-sided.”

Just as the sense of ‘the morning star’ involves a criterion of identifycation of a reference, so does the sense of ‘the evening star’. Suppose that the sense of ‘the evening star’ is given by something like the following criterion of identification:

CRITERION E: θ is the evening star just in case θ is the first celestial object visible in the evening sky just after sunset.

One who grasps the sense of ‘the evening star’ and thus grasps Criterion E will also have a one-sided recognitional ability. Whenever one is able to reidentify an object as the object which satisfies Criterion E, one is ipso facto able to re-identify that object as the evening star again. But there will be many situations in which the evening star is present in which a cognizer is unable to determine whether the object which satisfies Criterion E is present. Now both the recognitional ability supported by a grasp of Criterion E and the recognitional ability supported by a grasp of Criterion Majjhima Nikāya are abilities to recognize the very same object. But as long as it can be a discovery that the object recognized via the application of Criterion Majjhima Nikāya is the same again as the object recognized via the application of Criterion E, then it can also be a discovery that the evening star is the morning star.

We are now in a better position to appreciate Frege’s more general explanation of the possibility of informative identity statements. All such statements will involve two names which share a reference but differ in sense. When we have two such names, we have the same object denoted twice, but via distinct senses, and so via distinct criteria of identification of a reference. When the mere grasp of the two criteria is insufficient to enable us to determine whether the object which satisfies the one criterion is the same or different from the object which satisfies the other criterion, it can be a real discovery that the object which satisfies the one criterion is identical to the object which satisfies the other. Discovering the identity in question in such cases requires that we go beyond what is contained merely in our grasp of two distinct criteria of identification. When we have done so, we have discovered a non-trivial bit of further information about how the world stands.^[1] Not all recognition judgments are of this character. Some are trivial, for example, the judgment that the morning star is the morning star. Such judgments involve not the application of two distinct recognitional abilities to the same object again, but the application of the same recognitional ability twice.

Footnotes and references:

[1]:

According to K. Taylor ([1998] 2000), Frege seemed to believe that there are two different ways in which we might go beyond what was contained in the mere grasp of two senses in order to arrive at knowledge of non-trivial identity statements. First, we might empirically discover that, for instant, the morning star is the evening star. Second, we might derive such identities a priori via mathematical or logical reasoning.