I'm still learning DSP and referring to Oppenheim video lectures.
In that lectures, differential difference equation is obtained for IIR filter design, in Lecture 14.
$$\mathcal{L}[\frac{\mathrm d}{\mathrm dx}y_a(t)] = sY_a(S)$$ $$\mathcal{Z}[\frac{y[n+1] - y[n]}{T}] = \frac{z-1}{T}Y(z)$$
And using these two equations, difference equation $z-1=sT$ is obtained.
To calculate the z-transform of the differential, $y(n+1)$ is used. By using that term, are we making our system non-causal..? (As our equation depends on future values)
Thank you for your time..