Final answer:
Astronomy, according to Glaucon in Plato's 'The Republic', is a tool for fostering abstract reasoning and understanding the Forms, which are the higher truths in Platonic philosophy.
Step-by-step explanation:
Glaucon, in Plato's The Republic, suggests that astronomy should be used not just for the practical purposes of construction and measurement. Instead, it should serve as a means for the development of abstract reasoning and the study of forms. This educational approach aligns with the Platonic view of seeking the ultimate truths and the essence of reality through rigorous intellectual contemplation and philosophical inquiry, as opposed to relying solely on sensory experiences or practical applications. Astronomy, therefore, in the context of The Republic, transcends the earthly and ventures into the intellectual realm, encouraging the contemplation of the higher Forms, such as the Form of the Good, which is analogized to the sun in the famous Allegory of the Cave.