I have to critically asses this paragraph. Can someone please help?

I have to critically asses this paragraph.

Can someone please help?

Backward time travel will never be developed and used extensively by human beings at any time in the future. For if backward time travel were to be developed and used extensively then travelers from the future would be likely to visit our own time and times already past. But since such visits should be readily detectable and since we have no evidence of such visits we must conclude that such visits do not occur.