Final answer:
The Pisa Baptistery Pulpit by Nicola Pisano does not include a sculpture of "fortitude" that merges an interest in Classical art with Christian themes in the way described in the question; such characteristics are seen in other Renaissance works, specifically those of Michelangelo and Bernini, as well as classical sculptures like the Farnese Hercules.
Step-by-step explanation:
Answering the question of whether Pisano's Pisa Baptistery Pulpit includes a sculpture of "fortitude" that merges Classical art with Christian themes, we can affirm that such a fusion is a hallmark of Renaissance sculpture.
Recounting a similar blend of themes, we find that Michelangelo's Pieta and Gian Lorenzo Bernini's works, like the Baldacchino, display a restrained beauty and ideal naturalism influenced by classical sculpture.
However, regarding the Pisa Baptistery Pulpit specifically, it is not accurate to say that it features a sculpture of "fortitude" with comparable Greek or Roman attributes, as the pulpit created by Nicola Pisano indeed features virtues but doesn't directly depict Fortitude in the same way a Greek hero, such as Hercules, might be envisioned.
Instead, connections to classical art may be seen in other sculptural works. For instance, the Farnese Hercules by Lysippos was famed for its late Classical depiction of a muscular, weary Hercules, embodying the peak of human form in its exaggerated musculature.
Similarly, the Sarcophagus of Junius Bassus, while an example of early Christian art, depicts scenes with a classical style. However, these works are distinct from the narrative and virtue-laden sculptures featured in Pisa's Baptistery Pulpit by Nicola Pisano.