Objection 1. It would seem that the fruits do not differ from the beatitudes. For the beatitudes are assigned to the gifts, as stated above (69, 1, ad 1). But the gifts perfect man in so far as he is moved by the Holy Ghost. Therefore the beatitudes themselves are fruits of the Holy Ghost.
Objection 2. Further, as the fruit of eternal life is to future beatitude which is that of actual possession, so are the fruits of the present life to the beatitudes of the present life, which are based on hope. Now the fruit of eternal life is identified with future beatitude. Therefore the fruits of the present life are the beatitudes.
Objection 3. Further, fruit is essentially something ultimate and delightful. Now this is the very nature of beatitude, as stated above (3, 1; 4, 1). Therefore fruit and beatitude have the same nature, and consequently should not be distinguished from one another.
On the contrary, Things divided into different species, differ from one another. But fruits and beatitudes are divided into different parts, as is clear from the way in which they are enumerated. Therefore the fruits differ from the beatitudes.
I answer that, More is required for a beatitude than for a fruit. Because it is sufficient for a fruit to be something ultimate and delightful; whereas for a beatitude, it must be something perfect and excellent. Hence all the beatitudes may be called fruits, but not vice versa. For the fruits are any virtuous deeds in which one delights: whereas the beatitudes are none but perfect works, and which, by reason of their perfection, are assigned to the gifts rather than to the virtues, as already stated (69, 1, ad 1).
Reply to Objection 1. This argument proves the beatitudes to be fruits, but not that all the fruits are beatitudes.
Reply to Objection 2. The fruit of eternal life is ultimate and perfect simply: hence it nowise differs from future beatitude. On the other hand the fruits of the present life are not simply ultimate and perfect; wherefore not all the fruits are beatitudes.
Reply to Objection 3. More is required for a beatitude than for a fruit, as stated.
Source: Summa Theologica (New Advent)