How do Neoplatonic interpretations differ from original Platonic ideas?

Question

The Wikipedia entry on Neoplatonism says:

Neoplatonists would have considered themselves simply Platonists, and the modern distinction is due to the perception that their philosophy contained sufficiently unique interpretations of Plato to make it substantially different from what Plato wrote and believed.

What are these "sufficiently unique interpretations of Plato" that make Neoplatonism "substantially different from what Plato wrote and believed"?

In other words, what are the notable differences between Platonic ideas and their unique interpretations in Neoplatonism?

Answer 1

The traditional dividing line between the Platonists and the Neoplatonists is Plotinus (or, alternately, his teacher Ammonius Saccas, but as the latter left no writings, it amounts to essentially the same thing)-- in other words, about 600 or so years after Plato's death.

As the SEP Article on Plotinus states,

The term ‘Neoplatonism’ is an invention of early 19th century European scholarship and indicates the penchant of historians for dividing ‘periods’ in history. In this case, the term was intended to indicate that Plotinus initiated a new phase in the development of the Platonic tradition. What this ‘newness’ amounted to, if anything, is controversial, largely because one’s assessment of it depends upon one's assessment of what Platonism is.

That being said, Neoplatonism is an Alexandrian tradition, and as such, is largely syncretic. The degree to which this syncretism permitted later Christian, Islamic and Jewish philosophers to appropriate Neoplatonist thought is a large reason for its ultimate influence.

Answer 2

In other words, what are the notable differences between Platonic ideas and their unique interpretations in Neoplatonism?

This is a really good question, I would answer that since the death of Plato, Platonism has been and is the exploring of a present circumstance through the basic conceptual lense of Plato's metaphysics. Plato is what Foucault would call a "founder of discursivity", someone who has opened a space for the production of texts

A founder of discursivity in opening a disclosive space sets up a struggle of interpretations which starts a new line of history. In contrast to a scientific founder like Galileo, whose work is made obsolete by the new science he opens up, founders of discursivity never loose their importance for their interpreters.

So Neoplatonism is those who continue to produce texts in that space first opened by Plato, and it's marked by its similarities more than differences, its just that its neo, new.. Neoplatonism is less ablout modifying or changing the ideas of Plato such as Forms, and more about using the tenets of Platonic phisosophy to see a present point in time.