Hi All, So I'm at the point where my brain is numb. I've been struggling for the past few hours trying to understand causality. Specifically, I have an input-output relationship y(t) = x(|t|). Determining if this is causal has been very difficult. Causal means that the output at any given time t is dependent on either the current input (present) or past input. So, if I plug in 5 to my output equation, I just get 5. How is that dependent on the past? I'm being told that this system is NOT causal, I.E. dependent on the past, which is really killing me.