Periods of philosophical innovation are often followed by periods of consolidation (some would say, decline) when progress is sought by selecting features from different philosophers, regarded as opposed to one another, and combining them to form a unified whole.
Alternatively it may be claimed that the philosophers were not really opposed to each other in the first place, but when read properly may be seen to have been saying the same thing; a notable example of this is the neo-Platonist treatment of Plato and Aristotle.
Properly speaking, eclecticism is the former of these processes and syncretism the latter, but in practice the terms are used variously or even indifferently.
R J Hankinson, 'Galen's Anatomy of the Soul', Phronesis (1991); see p. 198, note 5
Also see:· neo-platonism