There are countless things that the LORD has done for His people, things that can be clearly witnessed and known. Recall how He led His people out of slavery in Egypt by terrible signs and wonders. Remember how He remained faithful to rescue His people even when they turned from Him. See the testimonies of His mercy and grace shown through Jesus, recorded for all to discover. These works were witnessed both by eyes that rejoiced at these works and eyes that refused to believe in them. By these things, people have decided to either praise God or reject Him.
There are people who think that if only God were to physically come down to earth today, people would finally know Him. But the truth is that He already did as Jesus, and even then there were many who witnessed His miracles – moreover experienced and benefitted from His miracles – and still did not believe. But for those who were opened to seeing God made flesh, they were blessed with great joy and assurance that God indeed had drawn near.
In our lifetime, God is still doing many great works as He did centuries ago. And He is doing His work within us His people as well. But are our eyes opened to seeing all the evidence of His glory around us? To all those with eyes to see, the psalmist beckons to come and see His awe-inspiring acts, that the LORD would be seen, known, and praised.